Some may argue that the Bible is perfect, and thus people are justified in blindly accepting everything it says. There are two points to make here:
1. How was this perfection determined?
How did you, an imperfect being with flawed cognitive capabilities (just like the rest of us), reach the conclusion that this book was perfect?
If it was determined by comparing with other writings/sayings, then you've just done the very thing you argued we shouldn't do. But suppose you hadn't compared the Bible with every other source. If there was just one source more perfect than the Bible, that would make the Bible imperfect by comparison. If that source was yet to be found, then that provides the argument for why we should never stop comparing the Bible with other material and other ideas. It should never be above scrutiny, lest we fool ourselves.
2. Where is the harm in questioning it?
If the Bible really was perfect, then surely that would be borne out in every test or comparison we might conduct. Thus there is no harm in forever questioning it, just like we should do with every book or idea.
If at some point we determined that the Bible was not in fact perfect, then we should change our belief. There are many Christians who do not think the Bible is perfect, so such a view is clearly not required in order to remain a Christian. I think the same applies to the words of Jesus.
By the way, if you are tempted to argue that we should trust the Bible because we cannot trust our own judgement or intelligence (i.e. Proverbs 3:5), that argument is self-defeating. If our intelligence and judgement were so unreliable, how would we determine that the Bible was trustworthy in the first place?
Was Jesus actually perfect?
Don't get me wrong. I think there are many sayings in the Bible attributed to Jesus that promote very noble and high ideals. To love one's neighbour without discrimination is indeed a lofty thing to aspire to.
But there is a tendency to have this one-sided, rose-tinted view of Jesus, rather than take in the full picture and think a little more critically. He was, after all, a man, and needed to eat and visit the bathroom just like any of us. No doubt he got food stuck in his beard from time to time. I suspect he made mistakes just like anyone else. He definitely insulted people and said nasty things, especially if the gospel accounts are to be believed. You may think he always showed love to his enemies, but if so he had an odd way of showing it. Threatening people in the temple with a whip would easily be enough to get someone arrested today. In fact it would have done back then too, which is why I consider that particular story implausible historically, but that's another matter.
Again, don't get me wrong. I think Jesus was generally a good man, if a little bit on the crazy side, and probably had good intentions. He was probably also fairly smart, although not smart enough to avoid threatening the Romans. For what it's worth, he either intended to challenge Roman authority, in which case he was at least partly responsible for his arrest, or he did not intend to, in which case he made a massive error of judgement. A mistake, if you will. But either way he left behind a legacy that has literally changed the world, and probably for the better (note that I do not claim that Christianity made the world better. Given the number of holy wars etc I think that is much less clear). His followers felt that he did not deserve his punishment. They also, apparently, remembered a lot of things he said and were moved enough to retell the stories, and eventually write them down.
Just a note on that. We don't have the original gospel accounts. They did not survive through time, or at least we haven't found them yet. We have small fragments from later centuries, and the oldest complete manuscripts we have date to the 3rd century CE. One could make the case that if any other texts were produced during that time (about other famous preachers, for example), we don't have them. The reason we have the gospels is largely due to the religion that formed in Jesus's wake (providing the motivation for people to make lots of copies of the gospels and other texts), not necessarily due to Jesus himself. It is not entirely clear to me that Jesus even intended to start a religion. If his followers had never come to believe he had risen from the dead, perhaps I might have ended up trying to convince Christadelphians (or Zeusadelphians?) that Zeus probably doesn't exist. History is written by the winners, after all.
Not the only one
We know Jesus wasn't the only such figure in his time. Christianity made Jesus popular, but it did not do so overnight. It was a minority religion even within the Roman empire until at least centuries after it started. However, there was another figure known as Apollonius of Tyana, whose description sounds eerily familiar. It raises many questions for sure, but there are no clear answers to them.
Biblical scholar Bart D. Ehrman relates that in the introduction to his textbook on the New Testament, he describes an important figure from the first century without first revealing he is writing about the stories attached to Apollonius of Tyana:
"Even before he was born, it was known that he would be someone special. A supernatural being informed his mother the child she was to conceive would not be a mere mortal but would be divine. He was born miraculously, and he became an unusually precocious young man. As an adult he left home and went on an itinerant preaching ministry, urging his listeners to live, not for the material things of this world, but for what is spiritual. He gathered a number of disciples around him, who became convinced that his teachings were divinely inspired, in no small part because he himself was divine. He proved it to them by doing many miracles, healing the sick, casting out demons, and raising the dead. But at the end of his life he roused opposition, and his enemies delivered him over to the Roman authorities for judgment. Still, after he left this world, he returned to meet his followers in order to convince them that he was not really dead but lived on in the heavenly realm. Later some of his followers wrote books about him."
Ehrman goes on to say that Apollonius was a real person and that his followers believed Jesus to be a fraud.
Wikipedia (The quote from Bart Ehrman is from his book, "Did Jesus Exist", pages 208-209).
Most people today have never heard of this man, perhaps because the religion that started in his name did not survive. Christians might be tempted to argue that Christianity survived because it is true, but they might be reluctant to apply that same argument to the other major religions of today, some of which are much older than Christianity.
The point I want to make here is that if Jesus was supposed to have been perfect, would we really expect such a tiny distinction to be made between him and other people? Would we expect other people to have been held in much higher regard than Jesus, even by (many) people who knew him personally? One of the Bible's central messages is that human nature is grotesque, desperately wicked, and worthy of death. If Jesus was indeed perfect, shouldn't that have been blindingly obvious to everyone? After all, the doctrine of the atonement rests on the foundation that there is some great distinction between the life Jesus lived, and everyone else! But in reality it reads like God penalised the entire human race over a very minor technicality.
Instead of showing us how Jesus was the perfect example of the way we should live, his followers emphasised his miracles, and occasionally his perceived wisdom (more on that later). These were the exact same qualities admired in many other people from the same era, including the Roman emperors (who also had miracles attributed to them)! Where was the great distinction between them? Is popularity the measure of perfection? Does perfection only exist if one has a religion start after they die? The way the Bible paints human nature, Jesus and the rest of us should have been at opposite ends of the spectrum, like night and day. Yet almost everyone who knew him couldn't tell the difference. Why was that?
I just think there is no case to be made here. The best you could do would be to argue that Jesus was the only perfect human and that many other humans were a very close second, most of whom were not Christian (and thus would not be saved by God)! This runs completely against the Bible's central message. Isn't it perhaps more likely that we should question the judgement of those who claimed he was perfect?
Those who made such claims were biased due to their belief in his resurrection (which, for almost all of them, was hearsay). But isn't it far more likely that people would mistakenly think a person rose from the dead, than that a person would actually rise from the dead? We should rule out the resurrection on probability alone. We will never know what really happened, but given the number of false resurrection reports throughout history (including in modern times), the probability of that one being true is so low it's just ridiculous to believe it actually happened, rather than that stories got changed and/or people were mistaken (as we are happy to conclude in every other case).
Was Jesus's advice perfect?
Many Christians (and Christadelphians) today refer to Jesus as the "wisest man that ever lived", surpassing Solomon. For what it's worth, I think the reports of Solomon's "wisdom" are even less credible than the gospels, but that's another matter.
But what did Jesus teach, and was it really the wisest advice anyone could offer?
Do unto others
"Treat others in the same way that you would want them to treat you"
Luke 6:31 NET
For the most part this is good advice. It is known as the golden rule. Jesus probably did not invent this saying, and he is certainly not the first to say something like this.
Possibly the earliest affirmation of the maxim of reciprocity, reflecting the ancient Egyptian goddess Ma'at, appears in the story of The Eloquent Peasant, which dates to the Middle Kingdom (c. 2040 – c. 1650 BC): "Now this is the command: Do to the doer to make him do." This proverb embodies the do ut des principle. A Late Period (c. 664 BC – 323 BC) papyrus contains an early negative affirmation of the Golden Rule: "That which you hate to be done to you, do not do to another."
Wikipedia
But while the golden rule is good, it's not as good as it could be. That is, there is a slight improvement one could make, which is another way of saying that the golden rule is not "perfect". The improved version is sometimes called the platinum rule.
"Treat others the way they want to be treated"
The difference is subtle, but very important. To paraphrase George Bernard Shaw, don't treat others the way you like to be treated, because they might not like it. Instead we should treat people the way they themselves would like to be treated.
Turn the other cheek
To the person who strikes you on the cheek, offer the other as well, and from the person who takes away your coat, do not withhold your tunic either. Give to everyone who asks you, and do not ask for your possessions back from the person who takes them away.
Luke 6:29-30
The flaws in this one should be obvious. It may well be good advice in some specific situations but in the majority of situations I can't see how this would help. It quite obviously plays more into the hands of the bully or the oppressor, while rendering the victim helpless. It is almost exactly the definition of "learned helplessness". It's the behaviour of a dog that, when attacked, rolls onto its back and hopes the attacker will lose interest.
One might hope that there's a god out there that will come to their rescue, but history and reality tell a very different story. The only ones who come to the rescue are other kind-hearted humans who show sympathy to their fellows and who violate this rule by standing up to the attacker. To those who argue that God motivated the helpers, I ask you what would be different if you remove God from the picture? And also, wouldn't that violate free will? If God was going to motivate someone to do something, wouldn't it make more sense to motivate the attacker not to attack in the first place?
So no, don't turn the other cheek, unless that is the only path towards de-escalating the situation. Be wise and read the situation as best you can, before choosing what you feel is the most appropriate course of action. In some cases you will need to defend yourself and/or others. In other cases you will need to report the offender to some authority and testify in order to promote justice. There are ways in which we all need to contribute in order to produce a just and fair society for everyone, and turning the other cheek is almost never one of them. Expose the wrongdoing and make society safer for others, so long as you're not unnecessarily putting yourself or others in danger in the process.
A good man, but still a man
I'm sure that to many Christadelphians, even the suggestion that Jesus might not have been perfect would be taboo. I'd use the term blasphemy but Christadelphians don't believe Jesus was divine (although they do think he is now). But this view is not rooted in reality. People who hold the view that Jesus was perfect do so purely on faith. That is, they have no good reason to believe it. They simply believe it because the Bible says so (which is definitely not a good reason).
I've shown several examples where we can easily imagine improvements to things Jesus is reported to have said and done. We can imagine a hypothetical person who spoke and acted better than the Jesus in the gospels. Perhaps you'll instead water down the claim such that Jesus was simply the "most perfect human that ever lived" (whatever "most perfect" might mean), or simply that he wasn't perfect but didn't do anything that God considered a "sin". This is either completely subjective or completely meaningless. If those who wrote the gospels wanted to portray Jesus as sinless they simply needed to omit any instance of him committing a sin. For what it's worth, I actually think they failed to do that, but again it's subjective. I just think that if people are expected to believe that he was somehow more than just some guy who said some nice things (and some not-so-nice things), then we're lacking any sufficient reason to believe that. You have to take the whole thing on faith, which you could just as easily do for Apollonius of Tyana, or any other historical figure you took a liking to. As long as the accounts written about a person were biased (and the gospels blatantly admit to it), you could share the same bias while believing the accounts were accurate.
I think it's fine to read Jesus's teachings and consider what he said. As I've mentioned, there are a lot of good elements in his sayings. But don't pretend he is infallible from the start, else you'll simply bias your own thinking and start excusing anything that doesn't fit your picture rather than seeing it for what it really is. We all know the danger of putting someone on a pedestal and pretending they are an authority on everything. So why don't we see it when the exact same effects are in play here?
It would do us all a lot of good to read and learn from the great teachers and philosophers throughout history. There are many of them, both religious and secular alike. Rather than be disciples of just one, we should read them all, take the best bits from each one, and form our own gold standard that guides us in our quest for a rich and rewarding, morally good life. Perhaps the reason you think Jesus was so exceptional is because you haven't read the works of others.
Jesus doesn't stand head and shoulders above the best philosophers in history. In fact in my opinion he almost disappears in the crowd. Just one voice among many. And if you're able to follow this train of thought further, that's how I view the entire Bible as well. A fantastic work of literature by human standards (for its time), but not the only one.