That seems to be a big part of it.

There's a widespread problem of anti-intellectualism and acting-out, including, in the US, by both right and left. Most of the learning feedback to that -- pointing out to people when they might be missing something or acting unfairly -- is ignored, except to attack those who point it out.

AFAICT, for various reasons, they're proud of being warriors for their beliefs, and anyone who sounds like they're saying anything differently is the enemy, and the only thing you do with an enemy is score points against them or hurt them, while trying not to concede anything that the enemy would claim as points or hurt you. It's a toxic recipe for society.

Coincidentally, recently I've decided even Fedi isn't safe from that (it's just different and fewer people doing ideological bully thinking), and have resigned myself that issues of substance can't be discussed there either. Maybe the only safe thing to post is cat pictures.

I think it's much less a problem with HN. Of course, over time you realize certain positions get downvotes that aren't flattering to the people doing it, and some annoying commenting behaviors, and not always all the integrity we'd like to see, which are relatively mild by social media standards. However, I'm also seeing occasional random individual actor extreme toxicity problems with HN. And I'm anticipating some related but different kind of problems from how AI-powered tools will be easily used with the corpus/firehose to play toxic games.