Ishaan Tharoor relays the messages in support of the nuclear deal from many Iranian dissidents and political activists:

Dozens of prominent Iranian activists, both living at home and overseas, have in recent days expressed their support for the successful passage of a nuclear deal between Iran and world powers, and urged lawmakers in Washington not to thwart the work of many months of concerted diplomacy.

This is consistent with surveys that have found broad support for the agreement from Iranians and specifically from Iranian dissidents. It is obvious that most Iranians would want to have sanctions relief, but it is also easy to understand why Iranians that want political and social reform would welcome an agreement that reduces tensions with other states and makes their country less of a pariah. They correctly see that the regime’s grip will be weaker than it has been once sanctions are lifted, and they also understand that their country is less likely to be attacked now that this deal has been reached.

Iran hawks would prefer to tear up the deal and subject Iranians to greater deprivation, and it is not surprising that most Iranians reject an alternative that would punish and impoverish them. Iran hawks will often profess sympathy for the Iranian people to advance their hard-line policies by claiming that the latter are aimed only against the regime, but again and again it is the people that bear the brunt of those policies while the regime has tightened its grip. The deal offers an opportunity to undo some of the damage that those hard-line policies have done to Iran, so it is natural that most Iranians welcome it.