Part of the problem with American righties and lefties is that they tend to make stuff up. The comment you're responding to is very likely an example of that, but in its own way it illustrates how they insert their talking points into even HN threads created to discuss how to get away from their talking points.
Viewed from that perspective, it's insidious even if it is completely fabricated.
If you read about "woke leftists cancelling [my tradition/Christmas]" day in and day out you start believing this stuff, even if it just started out as hanging out on certain subreddits for fun.
I don't believe everyone is as susceptible to this "convincing emotional content built on fear and rage" but it absolutely seems like a decent amount of people are. Especially considering these are usually the loudest voices in any debate.
That's the worst part about the American internet being so prolific in Europe. I don't think Americans understand how much their internet impacts Europe. I can only really speak for Northern Europe. But the impact is massive there, most content we consume after we learn english in our teens is American/English content.