I am sorry now that I was never too concerned about the music my kids listened to in the mid-60s and 70s. It was destroying. Parents should be very careful about cassettes and CDs they buy for their children.
Some of the music is immoral. Kids should be listening to music with messages like staying away from drugs or staying at school. There are some rap songs that are all right. Kids can dance to a beat but without all these sacrilegious things.
On the whole, I don't think it's bad. I am not into heavy rock, but mostly the music is no worse than what I listened to when I was growing up. I don't see any sense in warning labels on records or CDs because who reads labels anyway? Few people do.
The music is probably way too violent. I can't find any sense in the lyrics. If the music doesn't destroy your mind, it will destroy your ears. I don't think that banning music is the answer but parents have to be responsible for what their children listen to.