I have read several authors trying to explain Japanese atrocities. I think it boils down to the oldest of social conditions—racism and the feelings of superiority that accompany it. This inferior/superior dichotomy leads to mistreatment and atrocities. The Japanese simply were led to believe, and did believe, that they were superior in every way to their foes. I’ve read several who said Wainwright waiving the white flag in the Philippines reinforced the feelings of superiority and made treatment of Americans worse. This consequence of racism is by no means unique to the Japanese. Similar examples abound throughout history and current events.
they still have these feelings towards Brazilian Japanese from my understanding. The attempted reverse migration has been met with considerable resistance.