Do your research, he has never said that Iran doesn't want a bomb. He believes that it is not our right to keep them from building one. People argue that Iran will use the bomb if they have it. During the Cold War we were positive that Russia would use the bomb, but they didn't. Same goes for China and N Korea. As far as his other foreign policies go, why is it our resposibility to protect countries that have the means to protect themselves? Countries we protect invest their money into infrastructure, education, etc instead of military. Kinda funny considering we invest too much in our military and our infrastructure is falling apart.
In one of the debates Dr. Paul replied to Bachmann by saying that there was NO evidence that Iran was pursuing a nuclear weapon while the IAEA report states that certain activities of the program are ONLY relevant to developing nuclear weaponry. Comparing Russia to Iran in this instance is like comparing apples to oranges. Russia doesn't have a theocracy nor does it's government have a stated goal of wiping another race of people off the map. As much as I don't like Santorum, I agree with his stance that the Mutually Assured Destruction doctrine isn't effective against a culture that embraces martyrdom in pursuit of advancing its religion.
You can click here to read about Dr. Paul saying that there was no evidence of Iran pursuing a nuclear weapon before the Iowa caucuses. How about that for some research?
As far as military spending being too high, I'd argue that entitlement and other "mandatory" spending is the real culprit behind our failing infrastructure. Defense spending has not increased dramatically as a percentage of GDP while mandatory spending as a percentage of GDP has skyrocketed.