Please Clarify NWA

Would you please explain to me why it is acceptable for a black man to call himself or another black individual a nigger, as in the rap group NWA, which stands for Niggers With Attitude.

The manager of said group just died.

In this crazy world, that seems acceptable, but if a white man proclaims he is white he is automatically a racist.

If I as a white man, vote for or compliment Barack Obama, who is half white, I am an enlightened progressive. If I vote against him, or am critical of his actions, I am racist.

What is the label applied to a black man in my situation?