Why does it seem like most people are jerks?

I am aware that I am different looking. I mean I can look in the mirror and see it for myself but why do people have to be such jerks about it. Seriously, some people just stare with a mocking grin(usually men) and women just kind of scowl at me as they drive by. I've even had several people make rude comments. Do they not realize that I am a human being just like them and feel the same way that they would if I did this to them? I wasn't always weird looking either. I just kind of became weird looking in my late teens and early adult years. So I know what its like to be normal too. Which in a way makes it even worse. So why are most people such cold hearted jerks in this situation. Its like they feel a need to pick on whatever they consider different. I'm tired of the stares, the comments, I'm just so SICK of it all.