They’ve been socially conditioned into it. Remember that this is the same ‘internet’ culture that rewards headlines about one person “slamming” another. Redditors (and lemmings, and diggers, and just about everyone else on websites that use upvote/downvote bologna) upvote things that sound correct, are contrarian, sound like they’re from an authority, and especially that hit the target for the bot/ai/content farmer networks. A comment offering a subtle redirect or correction won’t get the ‘traction’ that a semi-angry, “I’m a X-and-Y on Z subject” comment calling you out for every single little tiny thing that is(n’t) wrong will. Also, anyone admitting they were, gasp!, wrong!!!, will get dogpiled on, and lose them the argument (which seems like that xkcd about internet arguing was not only correct in its time, but prophetic of an ever worsening future) which they absolutely will not stand for.