Should Iran be allowed to enrich uranium?

Should Iran be allowed to enrich uranium? It's a question I've been thinking about quite a bit over recent weeks. In the main, it seems to me that it's the wrong question. How about:

Should any country be allowed to enrich uranium?

I think that's a much more appropriate question. After all, if the permanent members of the UN security council all stopped enriching uranium, it would be much more difficult for Iran to argue that it has a right to do so.

Let's go further. It seems to me that the arguments against Iran being able to enrich uranium boil down to a suggestion that Iran sponsors terrorism, and can't be trusted with nuclear weapons. So, perhaps the question we should ask is:

Which countries have never sponsored terrorism (or similar), and hence could be trusted with nuclear weapons?

I'm not aware of any country which currently has nuclear weapons and has never taken part in terrorism or related activities. To take the US and UK as examples, in the 50s they apparently co-sponsored a group of mercenaries to support the coup that toppled the democratically elected government of Iran and installed the Shah as its non-democratic replacement. [Why did they do that? At the time, the Iranian government wanted to nationalise the oil industry there, i.e. BP.]

The US is also still the only country that has used nuclear weapons. At school, I was taught that this was necessary to end World War II. However, I now find out that at the time the US dropped the bombs, Japan apparently was already looking for a diplomatic resolution to the hostilities, and the US knew this because they had broken the Japanese encryption. [Why did they do it then? Hard to give a simple answer to a complex question, but the Hiroshima bomb was dropped two days before Russia planned to enter the Pacific conflict, something the US and UK were keen to avoid, to limit Russian influence in the region.]

So, I just can't support this idea what "we" can be trusted with enriching uranium, and "they" can't. When there's no way to tell the good guys and the bad guys apart, you have to treat everyone equally. That's one of those democratic principles, right?