Holocaust Denial.

Zvi Aharoni and Wilhelm Dietl make a telling point about this abomination at the end of their book, 'Operation Eichmann.'
They present the rather telling point that, although there are a number of holocaust deniers who are typically found in rightwing or extreme islamist circles - they all begin at an extreme disadvantage.
Neither Eichmann at his trial in Jerusalem nor the higher Nazis on trial at Nuremburg ever dared deny the fact of the holocaust - they merely attempted to diminish and dilute their own roles therein.