Why are people so judgmental of me, and others like me? Advice, please?

First of all, I'm more critical of myself than anyone else is of me. I'm a very introspective person who cares so much about the needs and feelings of others. I try to be the best person I can to everyone, trying not to judge or criticize anyone for who they are. If I catch myself out of line, I try to put myself back again. Unfortunately, I am a seventeen year old girl who is sometimes harshly judged/ rejected by others I accept. I swear! I am nice to them, but people around me are so fickle. It's like they don't want to be around nice people who actually respect them. why the hierarchy? I don't get it. My parents think I isolate myself, but the truth is I'm rejected to begin with. I suppose the person I identify with most is Sam from Garden State-I wish I knew more people like her. Advice? Sometimes I feel like just giving in and de-sensitizing myself! But I don't want to!