There is a difference between the bombing of Hiroshima and suicide bombing.
The bombing of Hiroshima was one event in the “total war” of WWII: both sides were going to do just about anything to each other in order to win. Of course, each side thought that it’s cause was justified and thus its methods were therefore justified. The enemy was evil because his cause was evil, not because his methods were evil (but of course there was war atrocity propaganda too). Here we have symmetry.
In the case of suicide bombing, one side is bombing civilians whereas the other side isn’t. The bombers say, “Our cause justifies these methods; besides, it’s all we can do.” The bomees say, “Your methods are evil and your cause is wrong besides. You’re total scum.” Here we have asymetry.
Looked at in terms of morality, deliberate attacks on civilians are wrong–period. Hence, the bombing of Hiroshima was wrong–period.
But we always get the same tired arguments: It ended up saving lives, and they did it to us first, and so on. No. Looked at from a game theory perspective, it would have been all right for the Japanese to nuke Los Angeles had they had the bomb, as it “would have saved lives, ultimatly.” But their cause was wrong! is the retort. But to them, of course, their cause was right. And so we nuke them and they nuke us, if they are able.
Hence, in game theory terms, the way not to be nuked is not to nuke. The Cold War manifested this principle; indeed, it took the Golden Rule to a new level in which we did not fight each other at all (well, not directly).
In the case of the suicide bomber–and I think this explains our disgust and disdain–we are already not bombing the civilians of the other side, but the other side is bombing us because of a “just cause.” They are not following the Golden Rule, they are not playing according to Game Theory.
The actions of both the bombers of Hiroshima and the bombers of the bus are both evil, but their position vis-a-vis their opponents is not. Hence the difference.