I would imagine the word, like many words can have different meanings given the context. Unlike the Suarez incident, which was clearly abusive in the context of the row they were having, Cavani clearly was using the word in ehat he felt was a positive way towards Bruno.
The issue is whether this word is appropriate in any context. And given the definitions I can find from a google search it seems that white people shouldn't be the arbiters of whether this word is racist, but arguing it's not doesn't seem to have any foundation.
It does seem that he is going to have to explain himself and face the consequences of his actions, and rightly so
I just hope United don't go down some insane Dalglishian route of defending a player at all costs.