The "niggers" versus "black people" thing might be attributed to Boondocks and its approach to the usage of the word.
Try even earlier than that:
However, as has been said previously, the idea of "good" black folks has been around for a long time. "Credits to their race" I believe they were called. Notably, Chris Rock cut this material from his act in part because he felt it was giving racists justification for using the n-word. I agree with people like Chris Rock, Aaron McGruder, the late Dwayne McDuffie, and Bill Cosby when they say that that the all too vocal segments of the black community holding up ignorance and criminal behavior as being "real" or "sticking it to the man" need to shut the fuck up because all they're doing is holding back the black community and American society as a whole. Appropriating racist terminology to draw the distinction is, while possibly an effective shaming tool and somewhat effective, ain't the way to draw that distinction. Especially if you're white.