Can anyone explain this to me in plain English?

You start off your question with the false premise that liberals think whites who voted against Obama were racists. Though this is a well establish falsehood in the right wing propaganda circles, it isn't true. Are you racist? I don't know. Are you an Asian American? I don't know. Are you dishonest? That I know. No, liberals don't think racism only applies to whites, but we also know that very few racists know what racism is.