The question presumes that the people being bombed were innocent, and that hatred and revenge are the most normal human reactions under such circumstances. Both assumptions are obviously false.
In the sense of being enthusiastically part of the war effort, mobilized to fight, and fully willing to kill and die for the Japanese emperor,
few if anyone in Japan was innocent during the war.
I have met numerous people in Japan who have talked about their wartime experiences and related how even as young elementary students they were marched and trained for war, using wooden guns in the place of real ones, and how they would have followed orders to kill invading American soldiers with sharpened sticks when the time came. Some of them even had a chance to act this out in real life. For example, near where I used to live, a US plane was shot down during the war, but the pilot was able to parachute out to what he presumed was safety. However, the people in the village saw his parachute go down. They cornered the US airman in a field and bludgeoned him to death. The body was then buried in a secret location to cover up what they had done.
The Japanese nation was prepared to fight to the end, and only gave up resistance when ordered to by their emperor. In that important sense, no one was innocent. They may have been duped by their government and its propaganda into supporting the war, but they were just as much part of the war effort as the men serving in the field, and saw themselves in that way.
Given how the Japanese army behaved in the Philippines, China, and other countries which it occupied or tried to occupy, it is highly doubtful that the US military did anything the Japanese military would not have done if they were trying to occupy the US, or if they had had the ability to take the war to US shores. As Sherman said, "War is hell." Right or wrong, the US military was just doing what it thought it had to do, and most Japanese people realize this.
At the same time, the question ignores the role of the Japanese military and political establishment in dragging Japan into the war to begin with. Putting aside the morality of Japan's wartime aims, it was Japan's failed political and military strategy, more than anything else, which resulted in the bombings and defeat. The overwhelming feeling within Japan after the war was that these men were to blame for what happened--not the Americans.
Finally, the most unproductive notion on earth is blind hatred.
The Japanese nation was nearly completely destroyed during the war, and for some years afterwards hunger, poverty, unemployment and homelessness were a fact of life for many Japanese. They did not have the time and energy to hate--they had to spend their energies on building a new life for themselves and their children. America was an integral part of this rebuilding. Without American aid, many people in Japan would have starved to death. In the light of all these things, it would be foolish to continue on living according to past grievances.
Once I was walking in the countryside and I met an old Japanese farmer. We began to talk and for some reason he related to me how he had been strafed by a US plane during the war while he was working on that same plot of land. He pointed to his body where he had been hit, and then noted that everything was OK now. When we parted, he actually thanked me--as an American--for coming to Japan and for loving his nation. From what I can tell, his attitude is far from unusual among the Japanese. War is a terrible thing, and terrible things happen in war, but one has to move on from the past and build a bright future.
Update: What is so often missing from discussions about the bombing of Japanese cities is context. Here is a link to a video regarding the Japanese bombing of civilians in Guangzhou in 1939:
China in WW2 - Terror bombing didn't start in Europe in 1939. Whether this justifies US bombing of Japanese cities is an open question. However, it demonstrates something of how Japan prosecuted the war, and Japanese expectations of how war should be fought. Certainly, in Okinawa and the Marianas, both Japanese soldiers and civilians expected no mercy, and were prepared to fight to the bitter end or to kill themselves rather than surrender, once resistance became impossible.
If one ignores the context, US actions during the war seem unreasonable and the Japanese seem to have been victimized by US barbarity. However, in context, the US desire to end the war by bombing cities rather than sacrifice untold numbers of troops in a full-scale invasion (an invasion that would have also resulted in even more horrific civilian casualties, given Japan's unwillingness to surrender) seems both natural and reasonable. All of the older Japanese people I have talked to fully understand this point. Alas, it appears that this point has been lost upon many younger Japanese and a great many foreigners.
