I disagree, given the high probability they were going to do it anyway. They built Natanz enrichment in secret, they built Arak in secret, they built Fordow in secret, not to mention the more recent violations of the NPT to which they're still a signatory. They've violated the NPT over and over and over again. Why would one more agreement make any difference to their clandestine program?

This is the thing Western liberals need to understand. The leaders of these despotic regimes don't think like you. They don't intend to adhere to the agreements like you would. Their psychology is different to your psychology. And you can't make a unilateral agreement with a party like this. The agreement becomes a weapon to creep forward and present the world with a fait accompli at a future date.