I will point out that Arthur Harris was not in command of US air assets, and that even if Churchill's analysis of Harris' intentions were accurate - which in point of fact it wasn't - Harris' intentions have nothing to do with US air assets or their deployment.
I will also note that Churchill's comments were made not only after Dresden but after the bombing of Dortmund, Essen, Chemnitz, Jena, Bielefeld, Hanover, Leipzig and Nuremberg. Several of these attacks utilized more aircraft and more ordinance than at Dresden against cities smaller than Dresden with lower-priority military targets than Dresden.
Is it possible that Churchill was referring to these instead of Dresden?
I will further point out that Churchill himself commissioned the Secretary of State for Air (the civilian oversight for the RAF and Harris' boss) to produce a report outlining priority military targets for aerial bombardment months before he wrote this letter to Harris.
Churchill received the Secretary's report on Jan 27, 1945. It mentioned Dresden as one of four key military targets that should be attacked as quickly as possible to assist Allied ground forces to sustain their post-Bulge positions.
By February 4th plans were drawn up to attack Dresden. During all this time there was no talk of inflicting terror or death on German civilians, but of the best way to prevent the successful redeployment of 42 divisions of German infantry and armor to the Eastern front, which was the purpose of the Dresden raid.
Nine days later, the Dresden raid took place.
Three weeks after Churchill's letter to Harris, Dresden was raided yet again, on April 17, to prevent the Nazis from rebuilding rail arteries across the Elbe to elude Allied forces.
That raid evoked no complaints from Churchill.
G&S condemns indiscriminate acts of war. You are defending them. Renounce and repent.
Nothing about Dresden was indiscriminate. Perhaps you should repent of twisting magisterial documents for rhetorical effect.
Your own words condemn you.