You keep using that term MAD. I do not think it means what you think it means.
You seem to imply that it's simply a policy of retaliating against any first strike with massive and lethal force. In fact, MAD, as a theory of nuclear deterrence, requires creating a situation in which a first strike from either side results in the total destruction of both sides, that is, mutually assured destruction. To be workable, this requires two things not present in the situations you describe (North Korea and Iran, or any other rogue state):
1. a rational enemy, i.e. an enemy for whom death is a bad thing. As much as American propaganda tried to paint the Soviets as godless monsters, they respected them as rational. Fundamentalists and North Koreans, not so much.
2. strategic parity - a nuke or two held together by duct tape, while certainly capable of causing much destruction, hardly gives anyone the capability of assuring the destruction of the US.
Yeah, the precise definition of MAD and the other policy options that result in the strategy I described are probably wrong. So what? The point is that it is policy as far as I know that any nuclear attack or specific threat to make one is to be responded to by a full-scale nuclear counterattack, regardless of how big or small the attacking country's arsenal is or what we think of their leadership. This is place for the purpose of deterring any attack, including by small countries. If it happens and we fail to follow through, then the deterrent is weakened, and the thinking of other nations about the viability of a first strike may change.
Why would you say Iran fails the first condition, i.e. that they aren't "a rational enemy"? They seem pretty rational to me. I can't be sure about North Korea, but for all the crazy news about them, they probably would behave like a rational enemy as well.
If Kim Jong-Un was faced with personal defeat (threat of losing power), I have no doubt that he would sacrifice his citizens to go out in a blaze of glory worthy of the Great Successor. In a sense, he's sacrificing his citizens now to support his lavish lifestyle, only he's doing it one starving farmer at a time rather than the whole country in one flash.
I'll defer arguing the rationality of the ruling power of Iran to someone with more knowledge. Bear in mind, my comment wasn't a slur against the people of Iran, but the government and military, i.e. those in the chain of command of potential nuclear weapons.
"Starving one farmer at a time" is evil but rational (and, it can be argued, is also done in some West-friendly countries). However, I very seriously doubt Kim Jong-Un would be able to "go out in a blaze of glory" in an apocalyptic scenario. Most likely, North Korea as a whole would act rationally and he would be taken out by a military junta before he destroys everything. No matter how evil he seems, he must have a rational entourage. Even Hitler had one. Stuff simply has to get done in NK; even if the only plan is "blackmail other countries to give us money", do you not see that's a perfectly rational plan?
As for Iran, I understood you were talking about their government. Nothing I've heard of them so far strikes me as irrational -- just hostile to some Western powers.
We must stop confusing "hostile" with "irrational", that's all I'm saying.
You seem to imply that it's simply a policy of retaliating against any first strike with massive and lethal force. In fact, MAD, as a theory of nuclear deterrence, requires creating a situation in which a first strike from either side results in the total destruction of both sides, that is, mutually assured destruction. To be workable, this requires two things not present in the situations you describe (North Korea and Iran, or any other rogue state):
1. a rational enemy, i.e. an enemy for whom death is a bad thing. As much as American propaganda tried to paint the Soviets as godless monsters, they respected them as rational. Fundamentalists and North Koreans, not so much.
2. strategic parity - a nuke or two held together by duct tape, while certainly capable of causing much destruction, hardly gives anyone the capability of assuring the destruction of the US.