"My nigga!!"
"The realest nigga I know!"
Ahem* ...I'm sure you've heard "The N word" used once or twice before, if not numerous times on a daily basis.
Some people are comfortable hearing this word, while some aren't - especially from white people, because it's taken as a racial slur, due to the origin of the word, ie from the term "nigger" which is a derogatory term for africans (including African Americans etc)
Looking at the history of the word, you'd see that the word "nigga" is an attempt to rebrand the insulting term given the africans, to make it less demeaning. Like an attempt to turn chains into arm accessories. But irregardless of this, it's roots are inherently based in the enslavement of a race and an assault of the human spirit.
I personally think it doesn't matter who uses the word. It's still a slur, it doesn't matter if you change "er" to an "a".