I don’t really buy the argument that Iran’s pursuit of nuclear weapons is defensive and nationalistic. If the Iranian mullahs were content to only torture, murder, and rob their own people, like Hosni Mubarak, they would have nothing to fear from the U.S. If Syria’s Assad had similarly modest ambitions, like Ghaddafi, he would also have nothing to worry about. Heck, Iran might even get U.S. foreign aid if they would just cool it. The Palestinians get plenty of it, from Europe as well as the U.S., some of which is used for reward payments to the families of suicide bombers. It is hard to arouse the Great Satan as long as you stay within your own borders, or, if you must venture abroad, at least only blow up Jews a few at a time.
Acquiring nukes and threatening to wipe Israel off the map are not really very effective defensive measures. I think they have something else in mind, but then I’m only going by their words and actions. Here is some interesting background at frontpagemagazine.com on the subject of Israel launching a pre-emptive strike against Iran’s nuclear facilities.