I don't know... from a very young age... I'm talking about like five years old, I've seen people act incredibly selfish and cruel. I don't particularly want to share a whole sob story here because doing so would make me feel a bit uncomfortable and I'd regret it afterwards... but let's just say that for a large part of my life I had people treat me like dirt. I would try desperately hard as a little guy to get people to like me and they would. Yet it was only because I was good at making them laugh. They liked me for selfish reasons; they liked me because it made them feel good. I would get too comfortable and then I would start getting personal, thinking there was a connection, only to have it thrown in my face and having people say that they didn't like me any more because I "wasn't as funny as I used to be" or that I got too serious and emotional or whatever... Just because I got comfortable and started sharing more of myself than just stupid shallow jokes. Over time I learned from it, I guess. I became very jaded and bitter and just stopped caring. Paradoxically then, I got more respect than I ever had before and it made me hate them all so much more. It felt like an affirmation of all the horrible things I thought about the majority of people. I moved on and followed some of the advice I posted for the other person and it helped me which is why I shared it. It would be a lie though to say, even in the improvement of my overall state of mind, that I see the average person to be any better than I did before.
So, yeah besides that, I've seen some messed up things in my life. Not all necessarily things that happened to me but I've seen enough to know that there are a lot of... unlikable people out there. I've seen more bad than good and that is strictly why I feel the way I do. Not to say by any means that there aren't good people, because there are and I think some of the people on this forum prove that fact in a great way. Still though, I just find it incredibly hard at this point to look at the majority in a positive light. But hey, what do I know? A large portion of my family on one side have serious depression problems so that might be to blame. *Shrug*
Edit: Just a quick example, one of my first memories of school is going on the playground and seeing a group of about five kids throw another kid down and start kicking him repeatedly under a tree while yelling mean things at him. I kid you not, they were probably like first graders, although I admit the memory is a little hazy. Still though... I really just don't like many of the things I've seen in my life.