You know, I had a history teacher in high school. He only taught the history that showed off America's history as noble, righteous, and struggling. He never really acknowledged, analyzed, or critiqued the BAD with the GOOD. He only taught the good.
When someone teaches something, and does so in a way that brushes to the side the despicable, horrible, angry, greedy, violent, murderous, and out-right hateful side of something, even though it clearly exists, they lessen their very words.
N.W.A. had a lot of messages. So does the modern-day of music done in the same vein. And a lot of these messages are blatantly revolving around greed, racism (or at the very least, the ideology of separate but equal, which is racist in my eyes), or simple hate. Maybe there are countless professors (9th Wonder included) who are teaching what's wrong with these aspects of the culture, but I sure don't ever see any of it.
Now, you can say that acknowledging this stuff makes you some kind of hip-hop uncle tom, but that's like saying if you criticize the policies of a flawed government you're somehow a terrorist or at the very least, not a patriot.