Hitler preached about
peace, making life
better, and all the same things Martin Luther King, John
Lennon, or Gandhi preached about. The difference between them was what in they practiced, not in what they preached.
Anybody can talk about
peace and making the world
better, no matter what their true intentions are. Hitler is an example of someone who could deliver convincing speeches about how and what he wanted to do to make the world
better, but it was his intentions he was acting on, not his words.