For anyone following along without clicking the links, it is important to point out that Magiver’s citation of the diplomatic correspondence does not say what he claims.
What it actually says is this:
You have both completely misinterpreted my statements, perhaps with intent. I am not suggesting that the Allies should have been conciliatory or offered a negotiated peace with the Third Reich and the martial government of the Empire of Japan, and I cannot see how either of you would even construe that from my post.
What I did say is that we discovered the horrors of nuclear weapons; not just their immediate destructiveness or even the fallout and residual radiation which may have impacts years or decades after initial use, but the fact that by dint of being able to release so much destructive power in a single device, we now have the ability for a handful of people to make and enact decisions which can end the lives of millions of people and destroy nations with no more than incidental review or check. And for decades since, we have proceeded as if the possession and threat of use of these weapons is just a normal and rational state of affairs. Some have even celebrated nuclear weapons as “keeping the peace” which is sort of like threatening rape to prevent women from them from having pre-marital sex.
In fact, while we haven’t always had the option of trying to negotiate a reduction of aggression or agree to restrain the development and buildup of ever-more destructive weapons (the Soviet Union under Stalin was arguably every bit as bad as Nazi Germany, and we couldn’t even figure out who was in control of what in China for decades), we’ve also often passed on opportunities to discuss arms reduction when it would benefit both powers involved. As much as the neo-con hawks today venerate Reagan and the military buildup (both convention and strategic) in the 'Eighties, Reagan’s real lasting legacy was the willingness to sit down with the leader of our avowed enemy, set aside differences in ideology and forty years of low-level and proxy conflicts, and have a reasonable and practical discussion about reducing these arsenals and preventing unintended or accidental use. That there is such political resistance (and largely by the same people who worship at the alter of The Gipper) is inexcusable.
This is what Obama was referencing in his speech, and with a minimum of obliqueness which should be evident to any reasonable person. Whether we “had” to drop atomic bombs on Hiroshima and Nagasaki (whether to defeat Japan or set the stage for the Cold War) is an academic argument; the fact is we did so, and the people on the ground afterward (including our own soldiers and journalists) saw the horror firsthand. This is something we should seek every reasonable way to avoid repeating, starting with reducing nuclear arsenals to a bare minimum required for national security, and encouraging other nations to similarly engage in nonproliferation efforts.
Stranger
I did not misinterpret your statement with intent. I responded to it as you wrote it which is perhaps not as you intended it.
Correct. I read it initially. Then I went back and read it again. Finally, I read it v-e-r-y c-a-r-e-f-u-l-l-y in case I was missing something.
Nope. Magiver’s cite does not support his claim.
You need (R)eading glasses.
If anything, the government of the nation hosting his visit asking him not to issue an apology would actually add credence to the argument that he then proceeded to not issue an apology, unless we just assume that it’s Obama’s policy to do the opposite of whatever any of his allies ask of him. 
I see what you did there!
(I think.)