Liberals start with the presumption that only white people who don't belong to the Democratic Party can be racist. So, for example, even if Jeremiah Wright can make it clear that he hates white people because of their skin color or if liberals take an explicitly racist political position, like suggesting that black people are too stupid and incompetent to get identification to vote, they can't be racist. White Republicans, on the other hand, are generally assumed to be racist by default, no matter how much evidence there is to the contrary.