Gang culture predates Hip Hop so I can't a agree, it goes all the way back to the 1960s, the gangs of today are the gangs of the 60s
Those older gang members also listened to funk acts like the Ohio Players, Parliament, Zapp etc, so that's not even necessarily true about what they were bumping, they listened to what is popular from their era
If crime went down and educational obtainment went up as Hip Hop became more popular, then people aren't doing what the music is saying
Hip Hop didn't create a subgroup of people that killed each other, gang killings were already happening, whether it was fighting over territory, drug money, pimping, etc
Music is a reflection of the culture of people's environments
The large spike in crime in the mid 80s to the mid 90s was the influx of Crack Cocaine in the community, what you see today is the lasting affects of The Crack Era
The same problem that created those gangs in the 60s is still here today, poverty; blacks are still the poorest group in the nation and thus have the highest rate of crime in the urban areas they live in
Blacks in wealthier areas listen to the same degenerates and don't have the crime or the ills of those without money