Hip hop/rap has its roots in the 70's and 80's anyway.
While the commercialized genre is of course trash (just as all commercialized music is, there's really no point even looking at 'pop-rap'), rap/hip-hop is a natural progression of poetry, which has in its more traditional form been marginalized over the past decades.... rap 'music' is more or less a merging of pure poetry (i.e. no musical accompaniment) what can be more easily considered 'music', which most (who don't listen to rap at least) would say requires to have rhythm, melody and harmony (which not all rap lacks in the first place). It's not my forte but there's no point in ridiculing it, just take it for what it is...
Further, pop culture is always about pushing the cusp of what's acceptable...
It's only natural that what would have 20 years ago been considered risque would today be considered docile and non-threatening, and thus you need to go further to get the same kind of reaction. Even with that considered, I've been in places where the radio station has been changed because the Doors came on, even today (that is, because the music was inappropriate as there were children in the room).
That said, I hate most modern music.
Things change, that's the natural order of things. The same apocalyptic prophecies of the future based on youth culture hash themselves over again every decade.
