I'm of Indian (not native american) decent and am into bdsm.

But to your question, I can only guess the answer (or part of it).
BDSM is shown a lot in Japan in those comics that it has almost become an accepted norm, so anyone embracing a bdsm lifestyle isn't so far of mainstream.
I think a lot of people in the world have either dom or sub tendancies, but due to social restrictions, taboos in society, religion, and customs, they may never even see the lifestyle that they subcontiously desire.

As for the white males part, I have no idea atm.