How come everyone just LOVES to hate on rap music?

I never used to like rap all that much but now it's my favorite music to listen to. It is great to dance to regardless of the lyrics. I can understand how some people might be offended by them but they shouldn't listen to it then! I'm really not into emo that much so I don't really know too many songs about that but the whole emo thing is a bit dramatic don't you think?