I would probably distance myself a bit from the wording of the question. The film uses humor in a very darkly effective manner. The nuclear policy of Mutually Assured Destruction (MAD) is shown to be laughable, but not something at which to laugh. I don't think that the film is suggesting that "we cannot help but laugh." Rather, I think that the film is bringing to light the flaws in the theory and thinking that escalated the nuclear arms race to a point where a "Doomsday device" is present in policies and actions of both nations. The film creates laughable governmental officials that are "entrusted" to keep the citizens safe and do everything but. The film does an excellent job of satirizing how the policy designed to eliminate our enemies and make us "safe" can actually result in more disaster than anything else. I think that the humor in the film helps to evoke the surreal nature of the modern Cold War setting.