That's because the comments are made by people who make comments on sites. It's a self-selecting set of people who
a) Have lots of time on their hands but nothing exciting to do with it (i.e. are unimportant)
b) Think people want to hear what they think (i.e. think they are important).
It's actually a good thing really. It's demonstrating that lots of the people with hateful views have crappy lives where they don't have a job that takes up lots of their time, where they don't have much stuff to do, and they don't have the money to spend the time that they do have doing something exciting; i.e. that people with hateful views have crappy lives.
It's cosmic justice really.
On the plus side, there's a simple solution to it: Don't read comments on sites. Ever.
I came to that conclusion a long time ago, but somehow haven't been able to break the comment reading habit despite knowing rationally that I should. I think I'm addicted to the rush of indignation I get when I read something I violently disagree with - but it's a really bad habit for my mental health.