This is a particularly ridiculous and odious notion--not that the Iranian regime isn't disgraceful and badly in need of a thorough, internal cleansing. It is ridiculous because the vast majority of Iranian dissidents have no intention of overturning the Islamic Republic, but want to reform it.
They are joined now by a significant slice of the theocracy, which is appalled by recent events and have no desire to live in a military dictatorship quietly dominated by the Revolutionary Guards. They have made it clear that they are opposed to foreign economic sanctions, to foreign interference of any sort. Mir Hossein Mousavi came out against sanctions a few days ago, on the ground that they would hurt ordinary people more than they would hurt the regime. What makes the call for regime change particularly tone-deaf and odious is history. Iranians--all Iranians--are extremely aware of past US meddling in their country's internal affairs.