[DavidShreder]

Granted, the Japanese Imperialists weren't so bothered by it apparently. The Rape of Nanjing is a horrific example of what humans are capable of if you brainwash them in a culture that convinces them that groups like the Chinese are sub-human. The Japanese had no problem killing millions of innocent people without any physical distance involved and without any survivalist imperative.

It was similar in Cambodia between 1975-79.

The difference between the two though was that the Cambodians were killing neighbors with different political philosophies or because they were "intellectuals".

There weren't years of brain washing and cultural adaptation.

I've only read a few accounts of the psycological effects suffered by former members of the Khmer Rouge and in just about every account all I've gotten was an attempt to mitigate responsibility or defelct blame.

Maybe level of civilization has something to do with it?

WWII Germans lived in one of the most advanced civilizations in the world, Cambodians, not so much.

Japan, as you said, was pretty well culturally desensatized to killing the "inferior" (as were the U.S. Calvary of the American West and the Conquistadors who ddecimated Mesoamerican civilizations).