[W]hat if the Americans had conquered a few Japanese cities, stopped their advance, and proceeded to shoot 140,000 Japanese civilians, men, women, and children (the number who died immediately or from injuries in the next few months from the atomic bombing off Hiroshima), explaining to Japan's leaders and its public that only surrender would prevent more mass slaughters? Would Truman's apologists have similarly justified this more conventional mass murdering as militarily and morally necessary? What if three days later Truman ordered American soldiers to shoot another seventy thousand Japanese men, women, and children from a second city? Would we not call such slaughters mass murder?Indeed, wouldn't we?
But why don't we process the dropping of atomic bombs on civilian populations that same way?
Goldhagen himself suggests a combination of nationalistic tendency to see one's country in the best light possible and a failure to draw distinction between the defining of an act and giving explanation and moral judgement of it. In other words, we know that Truman's intentions were not as murderous as Hitler's, therefore categorizing Truman's actions as mass murder doesn't feel right.
Going further in this direction, I would suspect that our mind's bias in the processing of ethicial dilemmas also plays a significant part.
Consider, for example, this thought experiment concocted by the philosophers Judith Jarvis Thompson and Philippa Foot: Imagine you’re at the wheel of a trolley and the brakes have failed. You’re approaching a fork in the track at top speed. On the left side, five rail workers are fixing the track. On the right side, there is a single worker. If you do nothing, the trolley will bear left and kill the five workers. The only way to save five lives is to take the responsibility for changing the trolley’s path by hitting a switch. Then you will kill one worker. What would you do?Marc Hauser discussed the whys and hows of such thought experiments at length in Moral Minds, but the gist of the answer of why actions that have the same consequences are viewed differently is because we are implicitly prejudiced against direct, physical intentional killing rather than indirect passive killing as a secondary consequence.
Now imagine that you are watching the runaway trolley from a footbridge. This time there is no fork in the track. Instead, five workers are on it, facing certain death. But you happen to be standing next to a big man. If you sneak up on him and push him off the footbridge, he will fall to his death. Because he is so big, he will stop the trolley. Do you willfully kill one man, or do you allow five people to die?
Logically, the questions have similar answers. Yet if you poll your friends, you’ll probably find that many more are willing to throw a switch than push someone off a bridge.
So when we think about soldiers going door to door, executing individual civilians we are naturally inclined to aversion, where as when we hear about a pilot flying over a city, pulling a lever allowing a bomb to fall out, and then flying off our minds are not quite equipped to feel the same inherent revulsion at this more indirect and passive form of killing; it is, for our "moral minds", an abstraction that doesn't register all that well.
And the abstraction becomes even easier to maintain when the consequence of the passive action is censored.
I would also suggest that this kind of dynamic is at work in the minds of those who somehow find Israel's actions regarding the civilian population of Gaza - e.g. killing Palestinian civilians at a rate several hundred times greater than Hamas killing of Israeli civilians - defensible.