We had already demonstrated the fire bombing of Tokyo and other cities (which killed more than our 2 A bombs).
True, but to leftists, fire bombing is somehow not as racist as American nuclear bombs.
Correct. And, most importantly, we only had two atomic bombs. It would’ve been foolish to waste one as a warning. Especially, as you point out when the Japanese had already disregarded traditional bombings of Tokyo.
And as we know, those two atomic bombs over Hiroshima and Nagasaki nearly failed to convince the Japanese to surrender. As we know the military attempted a coup to overthrow the Imperial government so as to continue the war.
Those atomic bombs saved millions of lives