Of course, I can think of several quick answers, but I believe there is a deeper answer that needs to be sought after, especially among white kids. Most young contemporary Rappers don't have long careers, usually because there's not much substance or long term thought involved. In fact, much like any other contemporary artist, to survive most Rappers who have been around for any length of time, are still around because they have toned their rhetoric down and become more inclusive of mainstream thought and ideas. Some have become movie stars, talk show hosts or record company owners. In most cases, they have toned their overall image down in order to be more acceptable to the general public.
Rap is a young person's game.
In either case, history demonstrates that rebellious youth, along with its' musical trends, is always eventually absorbed to some degree by the mainstream. I believe we shouldn't throw these kids to the curb. It seems to me that we must embrace them on a general level while letting them know that what they are producing is unacceptable and dangerous to impressionable minds.