I read recently that a group of peaceniks have protested that the Dayton Air Show, one of the best in the world, was planning to put on a display that they stated was an reenactment of the atomic bombing of World War II. After the protest the air show backed down and cancelled the display. While I don't love that the war required that an atomic bomb be detonated to win, it's obvious to most that it was necessary to win the war with the least loss of American life.
If one studies history it is obvious that the Japanese military establishment would not allow the rank and file citizens to give up without mass death on their part. Truman was advised that taking the main islands of Japan, based on the death toll of Okinawa would be in the neighborhood of one million American casualties. I don't think he had any choice. He ordered the bomb dropped and I think it was the right decision. The military establishment of Japan would not give up. They had to be made to do so.
I was appalled to know that Paul Tibbetts, the pilot of the "Enola Gay" which dropped the bomb on Hiroshima, was vilified for the rest of his life. He did his duty. It is instructive that he requested that he be buried without a gravestone so that it wouldn't be defaced.