It's not hard:
* They're trying to build nuclear weapons, and they're one of the worlds leading sponsor of terrorism (if not the sole leader).
* The country ran out of water, people started to protest their government, and were killed by the thousands (some say tens of thousands potentially more).
Water is one of the most basic human needs, if they're willing to kill their own people protesting for the most basic human need, what would they do with Nuclear to the rest of the world? I feel like people don't understand the gravity of Iran with nuclear.
Iran having nuclear will not end well for its citizens or the world.