You don't need to be black to be considered a rapper. It's sort of like how you don't need to be a country hick to be a country singer. In fact, there is even a country band called Bering Strait all the way from Russia. As for eminem... he wasn't the first mainstream white rapper either. There was the Beastie Boys and Vanilla Ice, who had an album go quadruple-platinum in one month in 1990.