Why the US was completely unjustified in bombing Hiroshima and Nagasaki

In seventh grade history, we were to write a paragraph about why the US was or was not justified in bombing Hiroshima and Nagasaki. This happened as a result:

     I don't believe the US had any justification for using the atomic bomb in Hiroshima and Nagasaki. They had already firebombed some 67 Japanese cities and overall devastated the Japanese. Yes, they would fight to the bitter end, but bombing gives people the most undignified deaths possible. You can't defend yourself if a) you don't know the bombs are coming, and b) they crash down before you have the chance to do anything.
     Bombing was one of the main reasons that the civilian death toll was higher than the military. Think of all the children either killed in the blasts or exposed to dangerous radiation that could give them cancer later on. They held no fault in the war; they may have been trained to obey their emperor, but they weren't Kamikazes or military personnel. They were completely innocent.
     And to the argument that the US gave them fair warning: if they'd truly given fair warning, there wouldn't be tens of thousands dead. If, somehow, some people had gotten out first, all power to them, but I truly doubt that the US managed to meet all – or even most – of the population with these warnings.
     The war also had quite a bit of racial prejudice from both sides. But I honestly believe that the US – which was, at that point, mostly European with some African and Native American (and the Europeans were and are the power group) – would not have unleashed the absolute horrors of the atomic bomb on Europe. Besides the fact that a great portion of Americans were ethnically German, the Americans also didn't routinely mutilate the bodies of German war dead. FDR didn't receive a letter opener fashioned from the corpse of a dead German! The US just didn't have many Asians; Asians were foreign, alien to them, so they had no empathy for them as people.
     The US also only had one location of theirs bombed in the war: Pearl Harbor, and that both had a comparatively low death toll and was quite far from the contiguous US. The Americans didn't know, for the most part, how it felt to be bombed. They got the terror part, all right, but they didn't know how it felt to wake up in the morning to find their business gone, their house gone, their family gone. They didn't know at all the feeling of not waking up in the morning.
     A combination of a lack of empathy, racism, inability to warn the Japanese properly, and inexperience with bombing led to the United States bombing Hiroshima and Nagasaki. There was no justification for ruthlessly taking so many lives, especially when considered that there were a mere three days between the blasts. (For heaven's sake, nothing ever got done in three days when government was involved!)