To just get back on topic, a lot of the stuff pushed onto people as "gansta rap" is a result of marketing. It pretty much all sounds the same, because that is what sells...no shocker there, that's music. For the most part it's just chest-beating crap, written by guys who grew up in suburbia.
The early gansta rap was pretty groundbreaking stuff because it spoke about how life was in some of the worst areas to live in america. That NWA-Straight out of Compton record is a brilliant, powerful piece of expression. You don't have to enjoy the music, but you have to appreciate the brutal honesty of it. There is no other record like it in this genre, all else pales in comparison, and just about everything else in the genre is crap/fantasy/cartoonish.
As for the white supremacist "music," no one takes this stuff seriously, and the punk/hardcore movement goes out of it's way to distance itself from these idiots. This is KzooMike bigoty, and there are very, very few venues where this type of music is tolerated.