Ron Paul, like the rest of the world, doesn't really want Iran to have nukes. Nobody really wants anybody to have nukes. However, Iran has a right to pursue its own interests, just as we do. When the UN gets itself in a tizzy and wants to put controls on our small arms industry and private ownership of weaponry, we start waving the 'sovereign nation' banner. Well, unfortunately, Iran is also a sovereign nation.
We have no legal right to decide what they can or cannot do within their own borders. Now, if we wish to declare war on Iran out of fear of what they might do, some sort of preventative war rather than a punitive war, let's just say so and drop any pretense of defense, moral high ground, or respect for sovereignty.
Or, we can go back to the way things are supposed to be: the threat of punitive nuclear annihilation. If Iran developes nukes, and uses them to attack us or our allies, we smoke or glass them all the way to Gehenna. Twice.