Forming impressions
It seems like the kind of people that usually go to hostile forums tend to have above average debate skills. Thus, they tend to form a low opinion of the debate skills (and thus general intelligence) of the other people in those forums, since those people will have average skills. Now, people tend to overlook logical fallacies supporting positions they already hold (which they can often justify using better reasoning), so they’ll also tend to overestimate the debate skills of people whose conclusions they share. Now, people who don’t go to hostile forums will tend to pick up a lot of their opinion of “the other side” from the people who do, because they don’t have any direct experience with the other side, but they do have exposure to the contrarians’ opinions of the other side.
Oh, look! Polarization! Insularity! Woah, where did that come from?
