The trouble is that someone with a very long view and a rather callous outlook could say that mankind "found a way" to defeat Hitler. Unfortunately, it took vast amounts of pointless death and destruction before things were righted (if that's the word), and fascism itself is still alive and well.
Personally, I think mankind has a sort of built-in curse: a very small quantity of people are sadistic, power-hungry psychopaths who simply can't care about anyone else, let alone the planet, and whose mentality is so different to normal that they might as well be a different species. Unfortunately, these people are hugely attractive to a much larger chunk of the population (I suspect between a quarter and a third), who will always follow the person who promises them revenge. It doesn't much matter who the revenge is aimed at or whether it has any justification. The point is that it feels good.
There's an old Onion joke story where two politicians have a debate. One gives sensible, reasoned opinions. The other promises to "kill the bastards". You can guess who wins.