Obama stood at a podium with the epicenter of the blast, the Genbaku Domu, in the background and said that he had "come to mourn the dead." While Obama mourned, there was one thing he did not do: apologize.
He said that "death came from the sky." No mention of why. Or who was responsible, as if it were a natural disaster rather than a crime perpetrated by actual people. Obama was either unwilling or unable to confront the truth and make amends.
Here's what he could have said to try to do so:
Seventy-one years ago, on a bright cloudless morning, an American warplane unleashed the most horrific and inhuman weapon ever invented, immediately imperiling the survival of the entire human species. This act of terrorism was the ultimate crime: a crime of mass murder, a crime of war, and a crime against humanity.
I cannot change that. But, there is one thing I can do as the leader of the nation in whose name the bombing of Hiroshima was carried out: I can tell you, residents of Hiroshima and the rest of Japan, that I am sorry. I am sorry on behalf of my government and my country. I wish an American President would have come earlier and said this. This apology is decades overdue. It is a small and symbolic act, but it is necessary as a first step for true reconciliation.
A nuclear bomb should have never been dropped on Hiroshima. The most important goal of mankind should be to ensure that no nuclear bomb is ever dropped again. Anywhere in the world. Ever.
The truth is that by August 6, 1945 Japan was defeated and had been seeking a conditional surrender for months. And American war planners knew this. They knew it because they had cracked the Japanese code and were intercepting their messages. 
Japan was willing to surrender under the condition that their Emperor, who was seen as a God among the Japanese people, be allowed to maintain his throne and not be prosecuted for war crimes. The Emperor himself called for "a plan to end the war" six weeks before the fateful day.  After so much unspeakable death and destruction, this reasonable offer should have been met with ecstatic celebration and relief.
Instead, U.S. officials disregarded it. They decided that it was necessary not just to defeat Japan, but to leave them utterly humiliated and disgraced. They wanted to demonstrate to their public that they could force another country to lay prostrate in front of them in complete submission. This is the mindset of terrorists, torturers, and sadists.
The United States joined with China and Great Britain to issue the Potsdam Declaration on July 26, in which they called on Japan "to proclaim now the unconditional surrender of all Japanese armed forces." These were terms they understood Japan could not accept.
Unfortunately, the use of the atomic bomb had become inevitable after the massive investment of time and treasure represented by the Manhattan Project. Military planners worried about "the possibility that after spending huge amounts of money ... the bomb would be a dud. They could easily imagine being grilled mercilessly by hostile members of Congress."
Historian and former Nuclear Regulatory Commission employee J. Samuel Walker confirmed that aside from "shortening the war and saving American lives, Truman wanted to justify the expense and effort required to build the atomic bombs."
That financial considerations and a self-interested desire for bureaucrats to validate themselves and protect their careers could lead to the single most destructive and cruel act in history is an abomination. It is a deep offense to the idea that people are innately moral, and it makes us ask how in a democratic society we can vest people with the authority to make decisions of such profound impact secretly and without accountability?
Walker notes that another consideration for using the bomb on Hiroshima was to put fear into the leaders of the Soviet Union and make them "more amenable to American wishes." Just six weeks earlier the UN Charter had been established. It included the demand that "all members shall refrain in their international relations from the threat or use of force" against other states. The drafters of the treaty could never have imagined such an unconscionable violation of their words so soon after the monumental pact had been written.
As horrific as the nuclear bombing of Hiroshima was, it did not occur in a vacuum. What no one in mainstream American political discourse has so far been able to admit is that not only was there no justification for the bomb, there was little justification for the war against Japan in the first place.
The war was the result of the notion, which first emanated from the Council on Foreign Relations in 1941, that the U.S.'s "national interest" called for a "Grand Area" that consisted of the Western hemisphere, the British Empire and the Far East, while assuming the majority of Europe would be controlled by Nazi Germany. This was translated into a policy that demanded a military confrontation with Japan for control of the Far East.