I don’t think religious fundamentalism is a modern construct, but fundamentalism does not need to be confined to just religion either. Many authoritarian cultures throughout history have used secular-based ideologies to oppress and harm/torture others too.
There are a couple of things that I wanted to address concerning this question’s details though . Firstly, knowledge is not absolute, and humanity will always be making new discoveries, changing the way we think, paradigm shifts occurring, and basically, always evolving. What we accept as a fact today might be discarded in the near or distant future.
Secondly, we can never know everything, and there might even be some concepts that in our current stage of evolution we can’t even conceive of, let alone to be in a position to evaluate and analyze them. People never have raw knowledge of anything, so we end up relying on our senses, in turn we create metaphors as the result of apprehending our environment with our senses, then we do the next best thing we can, speculate, wonder and many times create fantasies that help to shapeshift us. Ultimately, whether these thoughts are ‘rational’ or not, nevertheless, they are vital in how they play their part in how we obtain knowledge and advance ourselves by making new discoveries, pleasures and inventions that ultimately benefit humanity. The slippery slope here is bias, because since the reasons for this can vary, and if the bias becomes too strong, this is what ultimately will create fundamentalism.
Thirdly, we can’t be masters of everything, and even the most intelligent people lack knowledge concerning many subjects. Even some of the basics of certain scientific fields require at least several years of college education. Ironically some creationists, like Behe, probably know more about evolutionary theory than many of those who accept evolutionary theory as a fact (I’m not a creationist myself).
We are more advanced and evolved then we were in the past, but the thought mechanics are still the same. We laugh at the absurdities of mankind’s past. In two thousand years from now humans will be laughing at our own paradigms, and the pattern will likely repeat itself. Religion to me only becomes a problem when it becomes absolute, and scepticism to me only becomes a problem when it reaches the point of eliminating the metaphors that naturally accompany the human mind, and like I’d posted above, the metaphors which are ultimately vital for advancement. Dogmatism can take up many forms, and I even get into scuffles with those on ‘my side’ of the fence, especially concerning the new age drivel.
I’ll try to directly address your question now. I’ve found that there are basically two types of people who exist, and the divide isn’t political, or even religious. The real divide in my opinion is between people who are freethinkers vs those who are authoritarians (namely the authoritarian followers, the leaders are a different cat). What I mean by authoritarian (going by Altemeyer’s definition of the term) is that the approval of others is more important to them over anything else. Anyone who tells me this does not have a drastic effect on the way people think and process information is kidding themselves in my opinion. The war between authoritarians and freethinkers has existed before, during and after biblical times, and will likely continue to do so. Even indifference is the product of the information cascades that authoritarianism creates, even if the offenders themselves are not considered to be authoritarians per se.
Not all freethinkers will agree with each other on every topic either, but there’s still a drastic difference between a freethinker and an authoritarian in my opinion. All of us have biases though, and I’m also sure that none of us are freethinkers or authoritarians in an absolute form. Like today, the thought mechanics that existed ‘back in the old days’ are really not too much different, so I actually agree with the OP here, though my reasons are probably different for doing so.