Remind yourself that every single comment, post, video, update, whatever on the internet is already a selection bias for people who either aren't deterred by the fact that shouting into the void like that is inherently low value and stupid, or reject it and believe a tweet is inherently valuable.
IE, you should never ever ever treat an average of online discourse as a representative average of humanity. It is already a niche cohort before you get into specific groups.
That alone means you will see more of people who strongly believe their opinions, see more of people who like to hear themselves talk, see more of people who unironically state that "I am never wrong", etc. The comment format of the internet is also pretty much perfectly designed to support the absolute wrong kind of discussion if you want actual productive discourse.
Instead of two people going back and forth and building up that context of "Heres what I mean when I say X" and being able to ground discussion on that shared context, there is no shared context and every dumbass can leave a large drive by argument that is not in the same shared context as the rest of the conversation, leading to vacuous "point scoring" and "um akshually" and talking past each other.
Online discourse just doesn't progress, because there's nothing that drags my ass back here to respond to your point, like I would feel compelled to in reality.