Why don't you ask why anyone uses the word nigger. What difference does it make cause they are rappers? If you what them to take a certain position because it seems they are well read, why can't they throw it back in your face and say "because you are well read you should KNOW why we use the word nigga time to time." Why would their answer be any different from any else you had this conversation with in the past or future. They are just people. People that live in the same society and interact with the same community as you and I.(for the most part)