I'm fairly certain the racial propaganda against "Japs" is part of the reason for the lack of inhibitions in how the US dealt with Japan (namely the massive firebombing of civilian centres and the ultimate decision to become the first nation to use nuclear weapons and also the first nation to use nuclear weapons against civilian targets).
Humans who are taught to dehumanize others are capable of doing pretty horrible things.
The Russians also distributed plenty of propoganda pamphlets to their troops to show no mercy to the Germans (including citizens) as they faught their way towards Berlin. Propoganda comping from some high-ranking soviets, not just within the military. It was said to be a big contributing factor to their notorious behaviour afterwards.