Well, in some of my more cynical moods, I'd say that Germany, thanks to the 30 Year's War, the failed Revolution of 1848 and the unification under the authoritarian Prussians in 1866 resulted in all the free-thinkers, libertarians and egalitarianists being killed or fleeing to the US or Switzerland, which is why those nations became the paragons of democracy that they are now and Germany devolved into an Authoritarian cesspit... But that wouldn't be entirely accurate.
As for nobody else being capable of doing such things, I already said that the Japanese and Russians committed equally heinous acts, but then again, they were both oppressive, totalitarian regimes, much like the Nazis.....
No DEMOCRACY has ever done anything on NEAR that scale...
I'm not talking about countries, political systems or regimes, committing crimes. I'm talking about individuals. And any individual from anywhere, put into Germany, or Japan, or some aforementioned country, history or regime, at the time, would have had the potential to be a racist murderer. Unless you buy the theory from that 50s book I was talking about, that some whole nations of people, in their blood and genes, somehow are intrinsically more sheepish and likely to submit to some guy like Hitler. Although that's a racist statement in itself.
This is why I'm wary of anyone who can entirely dissociate themselves from the guilt of what happened in those gas chambers.