Thanks, I, too, believe we (all humanity) should remember the Atomic bombing of Hiroshima. But I have a different take on the event.
1) The city had been preselected as a potential target for the bomb due to military targets. But, as the OP points out, the real purpose was to demonstrate the devastation of the weapon for the purpose of bringing about surrender.
2) The bombing is not a stain of the "professed moral character" of our country. It was an effort to bring the war to a close, which might actually reduce the total number of deaths, including both Axis and Allied lives. Some, in a effort to disparage America, claim our estimate of more than 100,000 American lives lost in a land invasion of Japan is overblown to justify the bombing. Our experience on Iwo Jima and Okinawa indicated many would fight to the death, resulting in very high loss of life on both sides.
3) President Truman certain had his flaws, but I do believe he did his best to fulfill the vast responsibilities of the Office, something that cannot be said for our current occupant.