I suspect that obstinance this is rooted in strong black/white thinking. I don't really know how this works for these people and can't experience it myself because I have just one brain. While I am flawed in many ways, I am not flawed in that particular way. I don't really understand how this works.
I find that inability to understand qualified language is a decent marker. Note I said "I suspect that often", and not "I know this is always". Black/white thinkers will reply with something like "no, that's not true, here's an example where that's not the case: [..]" Well, okay ... that's what "often" means, further weakened by the "I suspect". But for black/white thinkers it's Highlander time: there can only be one (explanation).
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Bit of a related aside:
For the last year or so I've been using an extension to completely block people from Hacker News. The way this works is that I have two buttons: "bozo" to merely mark a post, and a list of marked posts in shown on the profile. And "block" to completely block them. Everyone has bad days, myself included, and I don't want to write people off for the occasional bad day.
But some people have a lot of bad days. And by "marking" people's posts some interesting patterns emerge. I mark a post for extreme black/white views on something like Israel and being pretty obstinate about it, and then 2 months later I see the same person with extreme black/white views on databases and being pretty obstinate about that. Are these two topics related? Not at all. But the same type of thinking is used: extremely simplistic black/white thinking with almost no room for nuance or "it depends".
Another person posted that thieves should be executed, "but if that is too extreme the chopping off of hands is also acceptable" (true story), and also rants about programming languages like they're 13, and rants about "wokeness".
The same person where a substantial number of their posts are rants about what inferior languages Go and Ruby are, also literally wishes death on politicians they disagree with, and claims "McCarthy was absolutely right" (which is a complete bollocks historical revisionism pushed by some people who are unable to understand "yes, turned out there were real Soviet spies in US gov't during the 50s, but there was zero overlap with the people McCarthy accused and he was just an unhinged nutjob who operated without any evidence against random people").
etc. etc.
What I learned from this is that by and large this kind of obstinance is not a "strong feelings about issue X"-problem, but rather a "brain just works in that way"-problem, whether that's due to black/white thinking, or something else.
There's an old joke: "A 9/11 truther, anti-vaxxer, sovereign citizen, and homeopath walk in to a bar. He orders a beer." Sometimes people are just misinformed on these issues and believe maybe one or two of them, but especially when they're knee-deep in nuttery it's just a thinking error.
I am still undecided if these people really are incapable of thinking in another way, or are just unwilling to do so. Or maybe there isn't actually any difference.