Of course, we cannot prove this in a scientific way, but neither rock and roll music nor hip-hop is actually the cause of juvenile delinquency. What tends to happen in cases like this is that older generations disapprove of both the behavior of the younger generation and the music they listen to. The older people then connect the two and argue that the music is the cause of what they see as the bad behavior.
Without scientific evidence, it is unpopular to say that music can actually cause bad behavior to occur. Without scientific evidence, it is more popular to say that the music reflects new values and new ideals rather than actually causing it to happen.