WW2 Channel (Indy and Co) Episode on Hiroshima and Nagasaki But it's a "war against humanity" special

If you accept that peace negotiations could have happened or that bombing a different location could have yielded the same results it's hard to justify which is why most Americans refuse to entertain the idea.

Peace negotiations implied a conditional surrender. The Japanese didn't want solely to preserve the monarchy, they wanted to preserve their government as it was. And most of the Japanese high command wanted to keep at least Korea and Formosa, these weren't acceptable terms. Even if the US didn't abolish the monarchy out of pragmatism they wrote Japan's new constitution and effectively putted an end to Japanese imperialism making Japan a democracy. Germany was given an armistice in 1918 and the end result was bad, that's why the allies were so focused on demanding unconditional surrender.