Of course they can, any race, gender, or sexual orientation can be discriminated against. Confused followers of intersectionality will try to argue that you can't be racist against whites because whites are in power. But, that's a dumb shit way of thinking and only encourages further racism. It's best to ignore those people and try to address bigotry and hatred wherever it may be.
Even if the power structure thing were true, it's still a racist question to ask because...which Whites are you referring to? White people have come from several distinct regions of the planet, it's not like we all sprouted from the same exact location. My memory may not be the best in the world, but I know the Irish, for example, were an extremely oppressed/marginalized people by both the English, and when they initially migrated to the US.
