Gil Lahav argues that, while the doctrine of MAD may not be worthless, it is inapplicable in the case of Israel and a nuclear Iran:
Those who favor or can countenance a nuclear Iran take comfort in describing the regime as rational. Rafsanjani’s speech reveals the true nature of that “comforting” rationality: Iran clearly understands that the “mutually assured destruction” that produced a Cold War stalemate is irrelevant to a conflict with a minuscule country like Israel.
Does Iran have any rational reason to destroy Israel? Unfortunately, it does. By achieving what no power could accomplish in 64 years, Iran would attain unchallenged hegemony in the Middle East. Such status would bring substantial benefits: skyrocketing oil prices, easier resolution of resource and border disputes in Iran’s favor and swifter exportation of Iran’s radical Islamic ideology.