During the WWI/ Russian Civil War the Germans occupied large chunk of Ukraine. Their military machine was strong and brutal, but otherwise they were remembered better than waves of Reds, Whites, Greens ravaging through Ukraine. Some Ukrainian Jews did not want to believe the rumors of German atrocities in the WWII and did not escape occupation and were exterminated, just because of this relatively positive memory.
Japan had its own distinctive culture as you rightly show, but in the self-inflicted isolationism, its effect on the Western civilization was low. They were perceived (note: perceived) as less civilized, so their atrocities were looked from the West under a prism of low expectations.
I hope you see my point. I make no excuses for anybody monstrosity, but in no other time a civilization as accomplished as German's fell so low and so quickly as under the Nazi rule.
Another point. Lots of Christians were killed during the WWII. The difference is that they were not killed BECAUSE they were Christians. Same as 300 thousand Jews soldiers of the Red Army were killed not because they were Jews, but because they were soldiers. But other millions of Jews and all Gypsies who did not escape were killed BECAUSE they were Jews and Gypsies. Same as Tutsi were killed by Hutus BECAUSE they were Tutsi. I find this difference being important.
OK....You win the entire point as this is an undeniable fact.
I don't beieve in any God but have no problem with people who do..... Lets hope civilized people everywhere can henceforth somehow escape the wave of Muslim barbarianism that is now among us.
Have a great day.