Other arguments have been made to further calm concerns of Iran becoming nuclear. One argument says that the US has it all wrong, Iran's quest is for peaceful nuclear energy for the Iranian people. Another says that the nuclear goal is really to help Iran gain more respect on the world stage (as stated by their own UN Ambassador). These points are at odds with each other - if the goal is peaceful energy, how would that give Iran any more respect as a country? Alternatively, Iran is already one of the most feared nations in the region, and they have plenty of trading partners among UN members (as evidenced by the UN's lack of willingness to support sanctions). So what kinds of additional respect are they trying garner exactly?
The fact is that if Iran really wanted to expand its energy resources and independence, they could build oil refineries to process all of the oil resources that are abundant naturally within Iranian borders into petroleum. Right now, Iran runs the (unlikely) risk being cut off from gas by UN sanctions. Some postulate that the Iranians are not interested in this idea as oil is not a clean technology. However, I've not heard any plans from Iran to stop drilling for oil once nuclear energy generation has been achieved, so clearly the concern for the environment isn't a driver in their quest to split the atom.
Bear in mind that a byproduct of even peaceful nuclear energy generation is plutonium. Over time it produces substantial amounts of Plutonium. Unlike Uranium, even non-weapons grade plutonium can be used to make a nuclear bomb - weapons grade Plutonium just makes a bomb more powerful. The technology needed to create a plutonium based bomb is well within the capacity of a country that can generate nuclear energy. So let's be clear, nuclear weapons capability is an unfortunate byproduct of allowing a country to develop peaceful nuclear energy. If Iran can develop nuclear reactors, they can in very short order create a nuclear bomb.
There will be those who will cast me as a Neocon or some such label and suggest that I am advocating war with Iran. Interestingly, this logic belies their own fear of war as a driver for accepting something that our future selves might regret. And it's worth noting that I am not in favor of any war, unless as a last resort. However, I do see the value in keeping such options as well as all others, available.