It depends... for me, credibility means truth. If your telling the truth, then you deserve all the credit you get, if you make good music. And your making crappy music, and lying to sell records, then you don't deserve credibility.

For example, Nelly had two proffessional baseball contracts before he started rapping, and he preaches his thug mentality, his drug hustling, his "thugness" on most of his music. His music just happens to be over-produced pop garbage.

Then we got Immortal Technique, who tells stories that people can relate to, talks about real issues like government and politics, whilst preaching that he had to hustle to stay alive. He also happens to be a great lyricist in terms of vocabulary and poetry, and his flow is awesome. He has a mic presence. He came from a poor country in South America, and most likely struggled in the American ghettos to survive because he didnt have much money as a child.

Immortal Technique = truth + skill

Nelly = fake image + no skill

Immortal Technique gets credibility, Nelly doesn't.