Agreed, but the US, with the largest nuclear stockpile in the world, is not exactly in a moral position to make such demands.
Not exactly, no. However, we still agree that it would be preferable for Iran not to have nuclear weapons, regardless of anyone else's hypocrisy on the matter.
With the Cold War gone, the US is in a position to unilaterally disarm itself of nuclear weapons and the rest of the world will follow our example, much like with chemical and biological weapons under the Nixon Administration. There will still be rogue states attempting to acquire them, sure, but the fewer legit stockpiles there are out there reduces the likelihood of proliferation, as most of the expertise is imported from the existing nuclear powers.
Ok, but you could just as well argue that with the Cold War gone, the rest of the world could disarm and then the US would be looking stupid if they didn't.