Those are facts- and to Hitler, any other belief did not make sense, and he could not rationalize why anyone would believe different. In his eyes, different was evil and evil needed to be eliminated.
Eliminating evil sounds like the right thing to do, doesn't it- especially when it becomes a majority view. Problem is, that when you seek to eliminate evil, you become the very thing you seek to stop.
Evil perpetuates itself and always will exist- hence the paradox of the Yin and the Yang. The two cannot exist without the other and sometimes cannot be told apart