Maybe I'm the only way that feels this way, but IMHO, I feel that "NIGGA" and "NIGGER" are 2 entirely different words, with entirely different meanings.
I, myself, have never used the term ''NIGGA". My folks never use it. It's just not our ''style''...(Oh yeah, we're all Mexicans).
Think about it this way:
If you are a black man reading this, and I were to walk up to your face and say, "Hi, NIGGER"...would you feel disrespected? Especially since I'm a Mexican.
Or, if you are a Mexican man reading this, same circumstances, but I was a black man, and walked up to you and said, "Hi, WETBACK"...how would you feel?
If a person of ANY RACE was to confront me and call me a wetback, I'd smash on that chump. Just as I'd expect to be called on it if I called someone a "NIGGER"...
My 2 cents...plus a nickel.
Peace