Like all genres, there's good and bad in rap/hip hop music. I myself am a fan of 'old skool' rap, where the emphasis was on skill of rhyming (and no-matter how much you hate rap, it takes a lot of skill to do it well) not seeing how many times you could say ***** or motherf***er per line. Modern rap/hip hop on the whole has become stale and dull.
Rap/hip hop culture has become the one of the most popular music types amongst teens/young people, no matter what colour they are, so that is used by advertisers to appeal to that audience.
Blaming rap music for violence is just like blaming marylin manson for the columbine shootings- it's an easy scapegoat and diverts attention away from the real reasons- bad parenting, goverment etc.
Sure, a lot of rap glamourises violent culture, and for some artists this is the life they know. Others just 'play' at it, and for kids it's exciting. Still, I don't think this causes crime, kids may think it's cool but their immediate environment is more likely to sow the seeds of bad behavior, not music. I think violent computer games are worse and no-one seems to really complain about those.
For me, theres nothing worse than being made to listen to country music, but it's still on some ads.
btw, switching from Coors is probably a good thing