At one point of my life , if I parted my hair the other way i was a dead ringer for Hitler. I dressed up as such one Halloween at a party in a bar. My friends were happy with that. Then a couple of Americans walked into the bar and I had to listen to a load of nonsense about how it was politically incorrect and an insult and, and ,and. Their tirade was interrupted by an Israeli couple who walked in, howled with laughter, bought me a drink and asked if they could take a group picture.
Go figure. I still have a brown shirt and the red armband but alas my hair is now the wrong colour!
I wish people were more relaxed, and the Americans had no business lecturing you. But the reality of the matter in the US is that there is no "innocent" riffing on an accidental resemblance to Hitler. (Speaking of which I hope you got rid of the stache...the Hitler upper-lip 'do was pretty ugly.)
A long time ago at my son's college, two white boys created a HUGE uproar when they dressed as black pop stars (complete with blackface and exaggerated buttocks/breasts). Some students felt that expulsion would be an appropriate punishment. The whole episode is now used as a "teachable moment" at orientation for freshmen.
Personally, I think the boys were ill-advised to dress as they did, and I would be furious if my kid ever indulged in such antics. (Thank god, he's got more class than that.) At the same time, I'm appalled that students of color - several of whom never even saw the costumes, only heard about them - insisted that they no longer felt "safe" on campus (please insert the world's biggest eyeroll emoticon here). And the notion that the boys should have been expelled for what was just a very tasteless costume boggles my mind.
Anyway, my point is that like it or not, and agree or not with the sensitivities involved, only someone living under a rock could be unaware of the fact that some people are liable to freak out at a Hitler costume. Should they? I say no, they should not. But in recognition of the fact that they would, and out of consideration for feelings that are not my own and might have a shred or two* of historical support behind them, there's no way I would dress as Hitler, go in blackface, or do anything of that nature.
* In case anyone is rhetorically impaired, that's understatement.