That arguments ("we're all black!") works until one considers African-Americans (capital Bs) as a unique and separate culture Which a lot of people apparently loath to do).

Since we're talking CULTURE here and not RACE, the it's very valid to wonder:

a) Was Bruno Mars actually raised within Af-Am culture? In Hawaii?

b) If not, then he's definitely copying the culture (not gonna go as far as appropriation, because he seems to cite his sources).