This isn't even a remotely similar situation. The biggest difference is that last time around, we were the only people with nukes and (agree with the decision, or not) it was a war ending use of nukes, with zero chance of starting a world war, nuclear or otherwise.

Among other things, those experimental first bombs were a totally different class of weapons from today's nuclear arsenal. There were conventional bombings in WWII that killed more people than the nuclear bombings.

The UK is the only other nuclear power to have detonated nukes on the territory of another country.

Completely irrelevant.

No, in fact very relevant. Not in the way the OP probably meant it though.