It would be helpful to your argument if you could find some references in Kurt Vonnegut's novel to the German V2 rockets which were described as "Hitler's secret weapon." Here is an excerpt from the Wikipedia article:
Beginning in September 1944, over 3,000 V-2s were launched as military rockets by the German Wehrmacht against Allied targets during the war, mostly London and later Antwerp and Liege. According to a BBC documentary in 2011, the attacks resulted in the deaths of an estimated 9,000 civilians and military personnel, while 12,000 forced labourers and concentration camp prisoners were killed producing the weapons.
The bombing of Dresden which killed approximately 25,000 people, mostly civilians, may have been a reprisal for the rain of V2 rockets which were also killing innocent civilians indiscriminantly. These huge rockets would fly over London and then fall when they ran out of fuel. Obviously, they could not be aimed at any specific targets, and they landed on schools, hospitals, and private homes with tremendous explosions.
Hitler hoped that these so-called "terror weapons" would somehow save him as Germany was being crushed between the Russians in the east and the British and Americans in the west. He may have hoped that the English people would be so terrified that they would ask the government to offer an armistice.
The Allies did not possess guided missiles, but they did have complete air superiority. It would seem seem natural to retaliate against the indiscriminant killing of civilians by missiles with indiscriminant killing of German civilians by bombers.
Vonnegut does a remarkable job of describing the horrors of the Dresden bombing, but it could be argued that the Allies could not put up with an endless bombardment of V2 rockets without trying to do something to discourage it. Hitler should have gotten the message that more retaliation would be forthcoming. The Germans often used drastic retaliation against civilians all over Europe and the Soviet Union for acts of rebellion. Naturally German propagandists described the Dresden bombing as an atrocity, but the Nazis were guilty of much worse atrocities, including the extermination of some six million innocent people in concentration camps.
If Germany had not surrendered in May of 1945, there might have been other fire bombings of German cities. General Sherman famously said, "War is hell," and World War II was the most hellish war in human history.