Story about Hitler is different, He is the attacker and he fired the first shot. His methods are clearly violent and unacceptable. How about the defenders of WW2. They have to be racist towards Germans to defend themselves. Do you expect them to be nice and reasonable with Germans when its war ? I hope not. there you have to give up your moral values when others do not respect them.
Dharmapala is not an attacker towards other races even though he is a racist. Can you show me a place he suggest sinhalese to burn muslim or tamil buisnesses, or to do any violent action against them. He is taking more peaceful path to give poor sinhalese some understanding about the situation they face. why they are in a sorry state and what will be the future if these habits continues. That is still racist, but better than Hitlers method. So you have to give some respect to dharmapala compared to hitler.