In Iran's defence, in spite of being attacked repeatedly with chemical weapons, not once have they retaliated with chemical weapons. This is in line with their beliefs which was formalized into a fatwa by the late Khamenei against nuclear weapons.
I would call that taking a pretty principled stand at a time when it would have been very tempting to redefine them.
Do you know what Khomeini did to his fellow leftist who toppled the Shah?
Yes (many).
Yes. Also what US planted Shah's SAVAK did to his political opponents.
So what is the point you are making, if any at all.