Racism is the subtle, seething mindset - not the act. Particularly, as a judge, if as a racist judge I sit in judgment of people of color, but don't call anyone names, make no overt statement of my beliefs, am I any less of a racist.
But to say that the guy is guilty of "the worst kind of racism" because he came dressed as Buckwheat to a party seems a little histrionic to me.
Every human being has biases, be they racial, religious, political, personal, or what have you. The best judges, in my opinion, are the ones who are aware of those biases in themselves and are capable of setting them aside in the courtroom.