Holocaust Denial is easy to refute. If the Holocaust did not happen it must be the case that every survivor of a Nazi concentration camp and every soldier who liberated a Nazi concentration camp conspired to lie about what was happening in the camps.Demonstrating why Tenure sucks. They also didn't fire that Nazi Holocaust Denier at Northwestern.
Race realism cannot be refuted because it makes assertions that are obvious to anyone who has had extensive experience with the three major races.
That is why those who fear the political implications of race realism try to suppress it.