Now that the Iran nuclear deal appears -- finally -- to have come to fruition, let's consider the two main lines of criticism against it.
- Iran will still be able to pursue nuclear weapons covertly.
- Iran continues to sponsor malevolent actors in the region.
Others will tread every step of spare ground on the first question (though it's worth noting that it would be much more likely to happen anyway if there was no deal). So let's talk about the second.
Iran's litany of foreign policy transgressions is long, but in this millennium, it mostly consists of providing aid and materiel to various regional governments and militia groups that Iran is friendly with, usually Shia groups. (The current list is Iraq's government and militias, Syria's government, Lebanon's Hezbollah, and possibly Yemen's Houthis.)
Here's the problem with pillorying Iran for doing this: everybody in the region does this. And not just this region: supporting allies with shared values -- or at least shared enemies -- is what countries do in unstable regions. The Saudis do it. The Qataris do it. The Turks do it. The United States does it. In some cases, Washington and Tehran support the same people, or at least oppose the same people. Demanding that Iran not engage in this sort of behavior is effectively asking Iran to not behave like a country.
Power abhors a vacuum. Iraq, Syria, and Yemen have become vacuums since 2011. Most of the regional players have, in one way or another, been sucked in whether they wanted to be or not, and all of them have supported exactly who you'd expect. Saudi Arabia and Iran have predictably backed opposing sides in all three countries.
Iran is not fighting an ideological crusade for world domination, as Israeli Prime Minister Benjamin Netanyahu would have it. It wants regional influence just like Saudi Arabia, Turkey, and others do. Supporting proxies allows these players to project power without actually fighting each other directly. It's not pretty, but if that's "sponsoring terrorism," there's a lot of sponsoring terrorism in the world.
Yes, gradually lifting sanctions on Iran will give it more money to engage in its foreign policy. Iran will continue supporting the Assad government, Hezbollah's attempt to save the Assad government, and Iraq's battle against Islamic State. Any Iranian government, regardless of its ideology, would likely do these things: if it didn't, it would visibly cede regional influence to Ankara and Riyadh. Those who are against Iran supporting its allies aren't against Iran's nuclear program, they're against Iran as a country. As nuclear nonproliferation expert Aaron Stein told Max Fisher,
So when we consider whether this Iran deal is a good one or a bad one, let's judge it by what it says on the tin: will it prevent Iran from acquiring a nuclear weapon? If it does that, it's a good deal. If it doesn't, it's not a good deal. A nuclear weapons-free Iran pursuing its regional interests would be pretty much what everyone says they want Iran to be: a normal country.