I think the key is the ‘rational actor’ part. If all parties are rational, then we can expect reasonable outcomes most times. My fear is that the same logic that drives suicidal islamic jihadists will find its way into the corridors of power in Pakistan or Iran and that faith will trump reason to all of our detriment.

But, I agree with your point: if Iran is a rational actor, then we should have nothing to fear from them having nukes as a security guarantee.

Assuming that the Iranian govt. is a rational actor, there is no reason that we have anything more to fear from them having nukes than we do Israel, or ourselves. All three countries just mentioned have radical religionists influencing their governments, but we haven’t seen any missiles fly yet. India and Pakistan are another good example of two countries that just hate eachother having had the good sense not to take it nuclear.

Why does Iran want nukes (assuming they do)? Because other people with nukes are constantly talking about messing them up, and if they have them, they will gain security.