[Ryzorian]

Japan has been around several thousand years, so thier history is full of things, both good and bad. Most nations that have been around that long have similer tails. The US has it's share cruelty as well, so it isn't like we can point fingers persay. Yes, Japan did some henious things in WW2, but they certainly paid a heavy price for it with the Firebombing raids and the Nuke hits. Some could even say those bombing runs were henious in and of them selves, so I suppose it depends on perspective.

Japan's culture has been dominated by the way of the warrior for a long time, certain things were exspected because of that, being an island unto themselves Japan was rather isolated from other cultures, so they wouldn't have a large reference of other viewpoints at the time. Sparta in ancient Greece, considering thier own warrior ethic, was easily as vicious as Japan.
Warrior culture in general tends to favor the strong willed over the weak willed. The Zulu's under Shaka were the same way. I dare say some of the American elite forces would be just as aggressive.