OK, I actually think this is an interesting question. So black rappers are producing mass media entertainment (music) which is intended to be listened to and most like sung along with by hundreds of thousands or millions of people. So the music people produce is for the entertainment of their audience, right? They are not sending private messages to select members of their own personal group. So isn't it a little strange to be peppering in words you don't want people using in your music?
Also isn't the usage of the word in a certain context racist? I mean if it's being used as a term of endearment in the song, and you are singing the song, which is an attempt to replicate the meaning and message of the original writer, how does is become racist? In the context of singing the song you are becoming the personal of the original author are you not?
I think its an interesting debate. I could easily see a case for both sides.