Children aren't taught how to behave by moralizing. We teach children how to behave by imposing negative consequences on them for engaging in behavior which we disapprove of. This prepares them for adult society, where the only rules are those which the people with badges and guns enforce. Choices and consequences, "if you chose to do this, these will be the consequences, and it's up to you to decide if it's worth it."

The same sort of approach can be taken with a figure like Hitler, or Mussolini, or any such individual. Forget about right and wrong, is that the sort of life you would want to have? Dictators don't have happy existences; it's a lot of paranoia, constant stress that your cronies, who you have no choice but to rely on, might be planning to kill you and usurp your position, and also constant fear that an opposition faction might be able to gather enough support in the military or the population to overthrow you and kill you in some horrible way. There are plenty of simple, hedonistic reasons why you don't want to try to be like those guys. It sucks!

Ultimately, I don't think there are a lot of people who want to do that sort of thing anyways, but we can ignore that for now. Why moralize, when you can just present clear consequences for the choices made? The latter seems like a much more effective way of influencing human behavior towards desired outcomes than the former.