But the difficulty is that once powers are in place they're difficult to shift. UK protests against the Iraq war were widespread and were stomped out very quickly with several checks and balances in place.

By 1939 Germany, you've got the old chestnut of complaints = unpatriotic and the SA/SS/SD/Gestapo plus probably a number of others I've missed off to control information flow and polish off any real dissenters. Even by then the mass murder hasn't started. Some might be feeling uneasy, but with the euphoria of easy wins and a reputation returned who'se going to worry too much? Perhaps the Jews did stop Germany ascent as there is a correlation between success and discrimination. And how many years of brainwashing have people had by 1939?

1941 - bigger fish to fry in Russia! Massive attacks against the Slav. The Brits haven't folded yet. Jewish rights? There's a Goddamn war on!

And so on. No nice "one day Hitler whilst kissing children and rebuilding Germany announced he'd off 6 million people, and called a referendum with international oversight."

You can try and charge people with Genocide but how would you do that when there is precious little if any admissible evidence and probably no witnesses any more. Or are we going to throw away Habeus Corpus to ensure some convictions? Better yet, let's torture them into confessing. That'll let them see how focused we are against atrocities.