This is not rhetoric from their politicians, leaders or propaganda. This is enshrined in their constitution (since Iran is a theocracy state it is Islamic ideology-based rule of law).
When a county A wants to wipe out a country B from existence on earth, country A can't have nukes. The nuclear countries Pakistan, north korea, India, may use nuclear weapon against their opponents. But they don't have this kind of goal that wipes out other countries from existence. North korea, if using nukes, even won't use them on south korea. Their nukes are used to against US and Japan.
Iran can't have nukes if they don't change their ideology which is to eliminate Israel from existence. But it does not mean we have to use military way to solve this problem, at least for now.