It's all about the message. I listen to Lecrae, Toby Mac, 116, Derek Minor, KB, Trip Lee, etc, on a daily basis because of the convicting and holy message that they convey. They've helped bring me closer to God, understand my own problems more and they've helped get me through the day, thus I am able to glorify God for them and because of them. If it glorifies God, then it is not a sin:
"So, whether you eat or drink, or whatever you do, do all to the glory of God." ~ 1 Corinthians 10:31
"All" means there's room for Christian rap, too.
I mean listen/read the lyrics of this and tell me if it's sinful or glorifying God?
[video=youtube;-cCTGSp1VzA]https://www.youtube.com/watch?v=-cCTGSp1VzA[/video]