When you challenge them to cite one racist thing trump has ever done or said, you get a blank look. "But everyone knows he's a racist" is a typical response.
Some will cite his comments about the judge in charge of the Trump University case. Apparently a white litigant who has adopted a political position widely disliked by the hispanic activist community is a racist if he points out the judge is a card-carrying member of that activist community. This after eight years of lectures from leading administration figures that justice is administered in a racially biased manner. I guess when the bias is against whites, we are not supposed to say anything.