Massacre from above minimized American losses.
But making shit stop, and stop right now? That can be useful as opposed to just.
I think we agree, I'm just saying this because I hear way too much about 'right' and 'wrong' with armed conflict. It's all wrong -ALL of it.
That said, had the bombs not been dropped, estimates ran into the millions for Allied casualties and tens of millions for Japanese (civilian + soldiers) casualties.
Ultimately it boils down to an issue of numbers (achieved by expediency).