It was terrorism and extremely unethical. No matter what the Japanese government offered, didn´t offer, refused or didn´t refuse - 99,9% of the civilians killed, injured and robbed of their family members and loved ones were not even involved in the negotiations.
Eeeehhh... I think you're being too general with this. The atmosphere of the time, the implications of a continued war, the nature and psychology of the enemy... there are too many factors to just brush it off and say we were being terrorists.
Start with the fact that we were ALREADY at war with the Japanese... inspired to fight by Pearl Harbor if nothing else (A case where the attackers were obviously organized with the country, unlike the current situation with 9-11 and Iraq. It bugs me when people compare the two. The 9-11 terrorists are/were a small group of radicals attacking during peace time, the kamikaze pilots had concrete ties to their government and were acting in the middle of a war.)
So we're already at war with some folks who by all accounts at the time were being some very evil buggers at the time, what with allying themselves with the Nazis and raping, murdering, and pillaging their way through China (not to mention the kinds of camps and experiments
they were putting people through, which make our internment camps look like fluffy daycare time. (I can find sources, please don't make me though. This kind of stuff makes me sick to call myself human.))
Add to that a different system of beliefs, values, and psychology. In general, Japanese soldiers would not surrender or let themselves be taken captive. It was extremely dishonorable in their minds, and every inch we ever took on the islands was covered in blood, theirs and ours. Death was more acceptable than surrender, and suicide an honorable choice, especially if one believed the lies told about what American forces would do to prisoners. Entire villages committed suicide at the encouragement of the armed forces, especially on Okinawa, where in the end the Japanese killed more Japanese than the Americans did. AND you gotta consider that Japan's cities were already being bombed, just with smaller bombs.
This was the situation presented to Truman, who had just been promoted after Roosevelt died in office. Truman didn't even
know about the bombs until after he assumed the presidency. Fact is, we only had the two bombs. More were in production, but it would have been quite awhile before they were actually useable. It was all still very experimental--that's why the Fat Man and the Little Boy were different after all. They were unique, no one knew which would work better.
Dropping the bombs on Hiroshima and Nagasaki was actually the biggest bluff the world has likely ever seen. Given the choice between taking out one city in a grand gesture of superiority or fighting a long, costly war on foot, Truman chose the grand gesture. Bomb one is dropped, does massive damage, offer of surrender is sent and refused. No one had ever seen a weapon that powerful before, and the thought was that the Americans had only one. So we dropped the other one, proving we had more. That was enough. If Japan had continued to fight, those bombs would have been wasted, those lives worth nothing.
The thing is, if we hadn't dropped the bombs, many, many more Japanese civilians would have died, as well as Japanese and American soldiers. It was terrible what happened to those people, but it was better than the alternative. Dropping the bombs was not an act of terrorism. One cannot deny that it would cause fear, but by that description EVERY wartime act is a terrorist act. The intention was not to create terror, but to display our overwhelming military superiority in a fashion that could not be ignored by the Japanese government. Destroying an island would not have been enough. Taking out a military base might have been, but there's no way to be sure. It had to cause enough public outcry to sway the officials into consenting to our terms.
And it did. It worked. It was a gamble, and we won. Woo.
I don't think anyone is proud of what happened. War is an awful, despicable thing. If you're going to do it though, you might as well do it right.