How to become less sensitive?

Sometimes I really feel like I'm the only one left who feels that it's wrong to make fun of someone because of their looks (especially weight). I know we live in cynical and shallow times, but I still find it unacceptable to be so cynical. Comedians, TV shows, the media, etc. Everywhere you look, there are people who are trying to push ons. I just find so much of today's humor mean and narrow minded. I don't know.... I just feel like everyone is becoming "tougher" and more shallow. I'm tired of being told that I should "lighten up". I know I probably should "lighten up", but my conscience won't let me. I hate being told that I have no sense of humor....