The war should have not even started, on the account that FDR cut off their oil. But I can't criticize Truman for making a controversial decision. An amphibious invasion of the Japanese homeland would have costed close to a million lives.
We have to remember that there are no rules in war. That is why it should be avoided at all costs. The goal in war is to annihilate your opposition as quickly as possible so they submit or relent.
You are laboring under the fallacious assumption that a land invasion was the only alternative to ending the war.
1. The war was already essentially won when we dropped the bombs. We were bombing cities like Tokyo on a daily basis. The Japanese had no industrial strength left to form anything that resembled a counter attack. It was only a matter of time before they had no other option but to capitulate.
2. The Soviet Union already had scheduled an invasion for the beginning of August. We didn't need to invade them considering the Soviets were going to invade anyways. This was essentially the reason truman decided to drop the bomb. He wanted the Japanese to surrender before the Soviet invasion, otherwise the Soviets would have claimed Japan as their own, and Truman was already working on a Cold War with the Soviets and din't want them to gain anymore territory.
In conclusion, the bombings, and the potential invasion, were unnecessary. We bombed them to end the war quickly before the Soviets could gain anymore strength. There was no other reason for the bombings. Jon Stewart is a wimp for retracting his statement regarding the criminal bombings.