I'm in favor of attacking Iran to keep them from going nuclear. But that is not my ideal solution to the problem of nutball Iran having nukes.
Debating the best "red line" that Iran might cross to justify armed responses to Iran's nuclear ambitions is a waste of time, in my view. I think Iran will surprise us when they go nuclear.
The best course of action is to destroy the mullah regime based on the "green line" of Islamist nutballery (Shia version) that they passed many decades ago.
Iran is dangerous and deadly without nukes. Keeping the nutballs from getting nukes should be Plan B to the Plan A of getting rid of the nutballs.
Or are you enjoying the preview in North Korea (which doesn't even have nuclear missiles yet!) of what a nuclear-armed Iran might act like? And North Korea doesn't have crazy Kimmunists around the world ready to act for Kim Jong Un the way Iran can call on Sunni and Shia jihadi-wannabees.
Have a super sparkly "sure, deterrence will work" day.