Some rap music is about violence. SOME! Stop talking about stuff you have no idea about! 99% of the hip hop I listen to is not violent.
You think most rap music is violent because of the very little hip hop you have heard. 50 cent and eminem might be the most popular and most played on the radio, but they do not represent the rest of hip hop music out there.
You want more violent music? Id say there would be SOME death metal or hardcore/gabba that is more violent. But I dont know enough about those genres to say.
I've been to lots of trance, hip hop, house, breaks, drum n bass and techno parties. There has been just as much violence at a hip hop party as any other party.