Caltrane,
Navigating the legitimacy of actions in war, particulalrly with respect to the impact on civilian populations, is always fraught with moral questions - if one bothers to ask them (and we should). That is one reason why there is typically an overwhelming amount of propaganda, intentional or otherwise, during times of war: to convince populations, at that time, that war is right, moral, necessary and that that those opposed are wrong and worthy of suspicion. There is a concerted effort to cover over the fact that huge numbers of people are being killed, and this can be done by converting those people into "others," or the "enemy" or any other label that serves as a wedge to distinguish or diminish their lives. It is an age-old act. You can even find this in the bible.
There are plenty of actions carried out during past wars that deserve a serious accounting, otherwise how will we will ever learn? You raise good questions about Pearl Harbour or the bombing of London; but what of the fire bombings of Hamburg and Tokyo, or the atomic bombings of Hiroshima and Nagasaki? A vast majority of the dead were civilians, many of whom had been convinced of the "rightness" of the war, not on the basis that the war would bring them physical improvements, but on the basis of unquestioned beliefs. Those who bombed them lived with the same thoughts, convinced that it was the right thing to do because the people below were the "enemy." Populations became nameless and faceless, ceased to be individual human persons, and the numbers killed eventually defeated the mental capacity to comprehend what those numbers actually made reference to.
The desire to set some adequate "measure" is realistic, but keep in mind it is always subjective: it depends if you are doing the bombing or being bombed, or choose to see the "rightness" of that bombing. Remember that we are still talking only about thoughts and ideas, not about the lives being affected or obliterated by the actions generated by those ideas. There is a difference between numbers on a piece of paper and shattered lives. If wholesale destruction of populations is the only perceived means to curtailing or eliminating feared ideologies, then we will find ourselves on a slippery slope towards mass murder and genocide. We may not think it possible, but there is always a probability for this sort of thing. History gives us the evidence.
If we think a different thought, we may see a different thing.
