I'm not saying it was entirely justified but yes, moral reasons were probably part of the calculations.
Dresden was mostly a British operation. The U.S. only participated in one if the four waves. As for the costliness of Dresden, Tokyo, & numerous other German & Japanese cities bombed into oblivion (some air raids in Germany consisted of over 1,000 planes), that's the total war mentality. It's a 20th century version of Grant & Sherman beating the enemy into submission. With Germany, all of their major cities lay in ruins & the country was in a shambles but they kept fighting. Finally, on April 30 Hitler committed suicide (hours after marrying Eva Braun) and the country still did not surrender until a week later. The Germans had inflicted similar damage on London, Manchester, Warsaw, & many other Allied cities and they kept the gas chambers at Auschwitz, Treblinka, etc going around the clock until the Red Army approached. To be honest, the Nazis barbarism justified this approach.
In the Pacific, the Japanese were even more brutal (Rape of Nanking, Shanghai, Bataan Death March, & many other examples throughout east Asia) and still fought on stubbornly. Their Samaria code prevented them from surrendering most of the time. I'm not sure if anyone noticed, but yesterday was the anniversary of Hiroshima and this Wednesday is the anniversary of Nagasaki. It took those two horrific bombings, plus the unprecedented intervention of the emperor, before they finally surrendered. Despite the high death toll, both were justified. The alternative was an invasion which likely would have cost 300,000 American lives and over 1 million Japanese. Those estimates might be low.
This is what is meant by total war and it's the main reason Europe has been consumed with pacifism ever since. It's also the reason all wars since WWII have been relatively small scale with deliberate efforts to avoid extremes but also mostly unsatisfactory outcomes even for the victors.
EDIT: I should add that the estimates for deaths in these dramatic attracts are all over the place and difficult to assess. I don't know if 100k were killed in a single night. Then again, Tokyo was a densely populated city then and many of the buildings weee constructed of highly flammable materials. It's certainly possible. This is what total war means.
“Incline my heart to your testimonies, and not to selfish gain!”
Psalm 119:36