Airborne Aircrew, I appreciate your reservations about the stabilty and motives of Iranian political leadership. I do not put as much stock in their standard anti Israeli sentiments as you seem to.
A far less stable nation, with a far less stable history and cultural baseline, is already in possession of dozens of nukes. Their explicit political foe, India, is the obvious target/deterrent subject for their nuclear arms. I refer to Pakistan. We (America) are on speaking terms with them, albeit our relationship is rocky. Their only saving grace at the moment is not being an explicit theocracy, even though the nation (such as it is) was set up as a homeland for Muslims by the British. Eff me, but we aren't even on speaking terms with Iran. How the hell are we to work this out?
I try to get away from the hyperbole and look at more practical problems, goals, and issues.
Iran's current political leverage is limited to sea denial, their ability to sponsor fifth column movements in a variety of places on the planet, and a modest amount of oil supply offered, or not, to the global market. Given those limitations, and their aims of being more of a power, they seem to make up for their deficiencies with added noise, bluster, and rhetoric as political tools. They also make the political appeal across cultural grounds to Muslims in an effort to form a "we and they" framework for persuading others of a mutual set of interests. (This is regardless of their actual motives and aims).
None of that is furthered by using nuclear weapons. All of the above is bolstered (at least regionally) by holding a nuclear deterrent.