And as to MacArthur, as you may recall he was more than willing to plunge the US into WWIII by invading China during the Korean conflict. He thought he had the right to be CiC and thought Truman would tolerate him voicing his opinions, contrary to the administration's, to the public at large and to Congress. Truman fired him and was right to do so.
My final thought on nuking Japan in 1945 is that they attacked us first, don't start something you can't finish!