A nuclear Iran would be a threat for those who have been sticking their nose in the country for about a decade now...so yes it would be a threat to oil as well. I know it'll sound crazy to NOT think about oil revenue for a second, but we're not the only one's who would be a risk. They've been having their holy war for so many years. Do we really want to introduce nuclear weapons into it?
If America would leave other countries alone. Stop invading, stop imposing sanctions, and stop spying we would have no problem with oil. Even better yet the United States can produce it's own oil. I would not mid higher prices if it would ease tensions with the Middle East. They can have nuclear weapons if the USA does.