Lemmy, reddit, 4chan... You find them all around. If you ask me, it's likely caused by childhood isolation. Kids who grow up in a tense environment or with certain disorders tend to be outcasts when growing up and this creates a bitterness towards the world.

It feels unfair that there is a way most people behave towards one another that you can not be a part of. And it's always easier to blame the environment than to look inward, find out what is causing these feelings and how to combat them. This is easily said when you're past your 30s, but a 7 year old kid does not have the capacity to do this level of self reflection. So the effects of being an outcast compound. At some point it just becomes easier to direct your anger at faceless strangers and avoid any kind of real social situations. And this, of course, also compounds.

But that's just my armchair psychology take on it. I have been somewhat of an outcast up until college (although not nearly as bad as some other kids I've met). College was an eye-opener for me due to the acceptance and positivity that was around everyone. I noticed quickly that the happiest folks where the ones who spoke mostly of things they liked. It's a cliche for a reason, but a positive attitude breeds positivity.