Even if one doubts the six million number put forth, the Holocaust was real. An extreme number of Jewish along with man many others were murdered and it is a fact. It's not the first genocide to have taken place on this earth and it was not the last, and sadly it will probably happen again; man is an evil beast and especially when in the game of politics and war.
However, there is evidence both from Germans and others along with plenty of sad and sickening film footage to prove it happened; anyone who doubts this is either quite ignorant or an idiot or a Anti-Semite.
And FWIW, a title, any title including one such as professor proves nothing, I've meet some professes that have left me wondering how they get through a day or how in world they passed a drivers test.
JMO