We never struck an alliance with them. There is no abandonment if there was no commitment to start with.
Backing rebel movements in Iran means war. It’s just a way to choose war.
Wars are dangerous. War with Iran would be a real can of worms. There’s no telling what course it might take. We could probably “win”, if we count as a win the thoroughgoing destruction of Iran’s nuclear weapons program. But that kind of “win” wouldn’t save the people the article is talking about, and any more ambitious agenda would be exponentially more difficult and costly to achieve. We could well fail. We could get them all killed.
Win or lose, the cost would be much greater than the cost of the Iraq or Afghanistan wars. I leave to others the evaluation of the chance that Iran will go ahead and use its nukes once it gets them. If we knew the odds were high, war with Iran, though a great evil, might possibly be the lesser evil. But how can we know that? And how could we convince the world that we act to prevent the greater evil, rather than because we like to play with guns?
It wouldn’t be easy, especially having got it wrong once before.