I agree that the United States should have dropped an atomic bomb on Japan. The biggest reason in my mind is not even listed, and it's the cruelty that Japan displayed throughout the war. https://en.wikipedia.org/wiki/Japanese_war_crimes The biggest reason for bombing someone is in retaliation due to their actions? I really disagree with this.
This sort of revenge mentality is never a good thing. 'An eye for an eye leaves the whole world blind' and all that...
Hypothetically: if this was the sole reason for dropping the bombs I would say that the US would be very wrong in doing so.
But I don't think this was the main reason. As has been covered by the others, I do think it was necessary to swiftly end the war and save more lives in the long-run.