You have just described the philosophy behind the fire bombing of cities, nuclear escalation, and mutually assured destruction - which given Vonnegut's Slaughterhouse Five was surely what he was talking about when he made that comment.
Fortunately the political leaders on both sides knew that they could never use nuclear weapons. Reagan was horrified and changed his policies, much to his credit, when he realised that the Soviets really were terrified of an attack from the West.
Even Khrushchev, who had a lot of blood on his hands, couldn't sleep for days after he had been briefed on what a nuclear war would actually mean - he only calmed down once he realised that the things would never be used by either side.
