So, smashing them into rubble then setting it on fire creating fire storms that wipe out everything is somehow better?
You are making a fallacy of presentism. That is, you are projecting current values back on those making decisions at the time in the past. Given the rape of Nanking, bombing of Rotterdam, bombing of London et al., by the Germans and Japanese, the US and allies had little compunction to not return the favor tenfold on their enemies.
Even then, the US was less likely than the Russians or British to just indiscriminately bomb cities. USAAF policy in most, not all but most, cases was to target legitimate military related targets and try to hit those with only misses causing collateral damage. Of course, given the state-of-the-art in the 1940's there were a lot of misses.
But when things went very right, the USAAF did what they advertised as they did here:
That's a shot of the USAAF in late 1943 bombing an about to open aircraft factory in Marienburg Germany. They smashed the factory with nearly 100% hits as the conditions for bombing were perfect. The factory never opened, and Hermann Göring who was scheduled to give a speech at the factory's opening the next day never got to...
The Luftwaffe extracted a heavy price shooting down over 80 bombers (800 + kia, wia, pow) between the four raids on the factory, but the factory was finished.
The only thing nuclear weapons did different was they did it in one shot at far less cost to the attacking side. Own losses were minimized, enemy losses were maximized. Seems like a good idea to me. In 1945, nuclear weapons were just a bigger, better, bomb.
Here's an interesting one. In early 1944, the US tried out for the first time using the GB-1 glide bomb against the German city of Cologne.
Over 100 were dropped miles from the city. The idea was to allow the bombers to evade being shot down by flak defending the city. The results of the attack proved so indiscriminate that the USAAF dropped the use of the weapon entirely for the rest of the war.