Here's the reason. Well, not really, it's just me presuming, but it's what I think of the whole thing.
The majority of the people on this website are teenagers. Or at least the regular posters. Myself included.
The majority of these teenagers are nerds. This means that they've most likely been bullied, rejected, whatever. I know, this happened to me. The way your mind reacts to this is to build up a superiority complex. It's just a way to rationalize things. They are bullying you because they are weak, and feeble minded, whatever.
Sadly, this extends to the rest of the world in time, and eventually, you just end up a jaded misanthrope. Thankfully, most grow out of it.
That's my take on it anyway. I used to be like that, hating humanity, or at least humanity in general, wanting to kill us all, all that shit.