Waltz appears to think that every single politician, every single military officer within reach of a nuclear weapon is a rational actor who will recognize that the terrible consequences outweigh any possible benefits. You need to be lucky every time. The bomb itself sends us the same message. Every nuclear weapon is a potentiality, a fission reaction suspended, waiting to occur. In the same sense that information wants to be free, or that water overflows its boundaries, every bomb is an explosion waiting to be let out.
Potentialities happen and over a long enough spread of time, they inevitably happen.
Note that if I were saying that a rational government, unopposed, would inevitably use the bomb, I would then be arguing for deterrence. There is no way of deterring a mad or self-deluded human. Hitler was not deterred from launching a World War by the patent absurdity of the notion that Germany could fight the Soviet Union and the U.S. simultaneously. The madmen who would use it could not possess it if they could not obtain the technology from more major powers. If we stopped making bombs, we could not sell the technology and we would not be vulnerable to its theft.