It was an evil act. War is evil.
Indiscriminate bombing of cities was what every single power who had the capability at the time did.
Here’s a good thought experiment. What other major power, if it had had the bomb, would not have used it?
Would Germany have used it? Duh.
Would the Soviets have used it? Also duh.
Would Japan have used it? Yet again, duh.
Would Italy have used it? Mussolini was DYING for a seat at the big boy table. The bomb is just what he would have needed to get it and for Italy to be taken seriously as a major power. You bet your ass he would have used it.
Would France have used it? As opposed to being invaded and occupied? Hell yes they would have used it.
Would Britain have used it? They were pretty much reduced to being the Junior partner of America by that point and everybody - even they - knew it. The bomb would have catapulted them right back into the front rank alongside America and the Soviet Union. And let’s not forget the Japanese had been utter bastards to them. They didn’t hesitate to firebomb German cities. Hell yes, they would have used it.
Would any of the smaller powers invaded, crushed and occupied have used it? Every single last one of them had they asked their citizens which option to choose, would have been forced by their people to use it.
EVERYBODY would have used the bomb at that time if they had it.