White people? Polite white people, at least, have long since learned not to ask They ask. They're just much stealthier about it. I get asked about once a week this question:
Them: Clausnitzer... that's an interesting last name, is it German?
Me: (Giving them what they really want) My father is of German decent and my mother Mexican.
Them: Oh, that makes sense.
Granted, this happens once a week because I am in front of a LOT of people every week with a business card in hand. Often, they'll only know me from email and my email address is my name, so they probably have a preconceived mental image of some arian fella.
It's normally done from a place of genuine curiosity and for that, I don't fault them.