Japan as a nation was not innocent, but that doesn't jusify the bombing either
Was it right? No. It goes against the principles of Just War Theory (which I subscribe to).
Indiscriminate weapons of mass destruction targetted at civilian population centers are unacceptable, even if they have the potential to "win" a war (such an acceptance would logically also sanction other forms of state "terrorism").
That perhaps the pilot(s) dropping the actual bombs or those supporting their dropping didn't fully realize the scope of the long-term suffering they would cause (how could they have?) does not lessen the evil nature of the act.
War may be hell, but human beings are still moral agents, even in war, and so their actions still can be judged according to moral principles. Recognizing the fact that in war much morality is tossed out the window in favor of expediency (or simply because it isn't as monitored and actively punished as in peacetime) is not the same as condoning such behavior (giving soldiers, generals and presidents carte blanch in wartime) or acceptance of moral relativism.
I could go into more detail if/when I have time, but I presume my opinions on the matter are already well known...