[U]nlike [Andrew] Sullivan, I don't believe American policy toward Iran should be dramatically affected by the ebbs and flows of Iranian unrest. I've made the case before, so I'll keep it shorter here: if Iran gets the bomb I believe it will enable the regime to crackdown on dissidents with never before seen impunity. Thus, to accept a nuclear-armed Iran and hope for the best, as Andrew seems resigned to doing, strikes me as wrongheaded and harmful for everyone invested in a better Iran--both inside and outside of the country.
Larison isn't so sure:
Kevin Sullivan argues that “if Iran gets the bomb I believe it will enable the regime to crackdown on dissidents with never before seen impunity.” This is possible, but I’m not sure that the two are all that closely linked. At present, Iran can already crack down on dissidents however and whenever it likes with impunity, and I don’t know that acquiring a nuclear weapon would add much to its willingness or ability to engage in such crackdowns. Outside intervention on behalf of Iranian dissidents will not be forthcoming anyway, so even the nuclear deterrent a bomb would provide would not make much difference.
The dissidents themselves disagree with Sullivan. I share Larison's skepticism. What the nuke does is balance Israel's regional hegemony and will allow Iran leadership to continue their harassment of the Jewish state - and Sunni Arab states - through proxies. I agree that that is a bad thing. I just find all the alternatives much worse, from the point of view of the interests of the United States.