Why are people so mean and hateful?

All you can do is be happy! Don't let other peoples unhappiness effect you, so that you remain happy. And try and surround yourself with like minded people. Every time I come across somebody who is rude or what have you I think to myself that they must be having a really bad day i.e. death in the family, brake up, kid crashed their new car.....whatever. and that usually makes me understand and feel better. And if I come across people like that I think of that and try and make their day happier, by even something as small as smiling at them!