Essentially all of the analysis over the Iran nuclear deal paints Iran as the transgressor. And indeed, Iran supports terrorists. Iran supports Bashar al-Assad. Iran is an aggressive power that seeks to influence other nations through violence.
Now who did they learn these horrible, deadly, destabilizing habits from? Oh, right, the United States of America, the United Kingdom of Great Britain and Northern Ireland, Russia... which is to say, the other members of the Six Party Talks (except China).
The Allies of WWII are the abusers in this relationship. Iran is the victim. Western governments overthrew the government of Iran twice in the 20th century. Why? The first time, during WWII, it was oil. The second time, after WWII... it was also oil. In both cases, the Western powers considered Iranian sovereignty a threat to their control over Iranian oil. In both cases, they put Mohammad Reza Shah Pahlavi in charge as a friendly puppet who would agree to unconscionably one-sided oil concessions. British Petroleum (actually its various predecessors) couldn't have Iran trying to actually audit their books, after all. That would establish the precedent that Iran had anything to say about how its own oil was extracted, refined and sold.
When the revolution finally came, of course hardliners won out. Everyone in Iran knew at that point that the US and UK had acted in bad faith, were acting in bad faith, and would continue to act in bad faith. Eisenhower and Churchill had done their level best to prevent democracy from taking hold in Iran. American and British governments have never once, in the past 100 years, accepted the principle that Iran has the right to control its own natural wealth on its own terms.
So of course stridently anti-American, anti-British hardliners won, and refused to play nice with the West. If they hadn't, the CIA and MI6 would have been right back in Iran staging yet another coup.
That is why the West and Iran are enemies. Not because of what Iran has done. Because of what we have done. This deal is not a chance for Iran to redeem itself. It is a chance for us to redeem ourselves. To abandon our unjust and illegal hegemony over Iran.
We're the ones that should be thanking Iran for the chance.
P.S. Israel has nukes and is just as belligerent as Iran. Why no sanctions on Israel?