This word is racially offensive, and to justify it as acceptable because it's rap music is ideological nonsense.
I'm not justifying it.
With any word, it can have racist connotations, or not.
The usage of the word 'black' could have had racist connotations at one time, but that seems to have rescinded.
There were idiots who reduced the argument to wanting to remove the word 'black' from the vocabulary, as in blackboard, blackmail, etc., which was absurd.
If a black person uses a word to address a friend, who is also black, it may not be racist or offensive. But if the same person used that word to a stranger, it could be construed as racist and offensive.
It ought to be an individual (or organisation) who decides whether they wish to use the word or not, but there are social pressures. That individual or organisation needs to be aware of, and take notice of those social pressures.
There are usages of familiar expressions in different languages that would be considered bizarre in other cultures, e.g. mon petit chou = my little cabbage or my duck = mon canard. I'm not sure of the relevance to this discussion, but it's context that determines whether a word is offensive or not.
It's just music, If Adele brought a song out with this word in, you would be demanding its removal.
Would I? I doubt if I'd be aware of it.