i can’t speak for all multiracial people (or anyone else for that matter). but personally any question that doesn’t pretend to be something other than it is is fine. if the thing you want to know is someone’s ancestry or ethnic background, then don’t ask “where are you from.” that’s all.
also, still not speaking for anyone else, but i’ve gotten pretty numb to people being racist towards me, because i decided that if someone’s going to judge people by their race (or anything else they didn’t choose for themself), then there’s no reason to care what they think anyway. though i will mock and ridicule racists for the sake of others who experience suffering from racism. especially kids.