To say that the holocaust was objectively wrong, is to say that the holocaust was wrong even though the Nazis who carried it out thought that it was right, and it would still have been wrong, even if the Nazis had won World War II and succeeded in brainwashing or exterminating everybody who disagreed with them, so that everyone in the world thought that the holocaust was right and good. To say that the holocaust was objectively wrong, means that it's wrong regardless of the outcome of World War II. The premise is that if there is no God, then moral values or duties are not objective in that sense.
William Lane Craig
ethics, morality, philosophy