That's as stupid as color-blind casting in movies. E.g. non-white aristocrats in the courts of medieval Europe, instead of making a movie about non-white people that's historically true (or as true as Hollywood history can be
). There were kingdoms and empires in other places than Europe, with no white people in them. Why not make a movie about them?
Or make a movie about alternate history. Steven Barnes has a series of books where the aristocrats are non-white and the slaves are white, because the history in their world went a bit differently than in ours. Such a story would make a great movie.