On the internet, people either show who they really are or who they want to be. Some people are dicks in real life so they are dicks online. Some people are nice in real life but since there's little reprecussions online, they use this opportunity to show their asshole side. And other people are men that want to be women, cool, or sexy space ship captains. It's a really diverse mix of personalities.
I try to present myself as real as I can be (this is my chance to be the person I can't be in the real world where I have to act hard, scary, and professional) and say the things I can't say in the real world (secrets, opinions, etc.) so I wouldn't dream of trying to be a dick to anybody. But I guess there are those that can't help themselves.
