You wrote that he never intended to carry through. This means the threat was a joke. You don’t joke about wiping an entire civilization.
Now you said it wasn’t a joke and just a threat. You don’t threaten and you don’t joke.
Pffft. There is absolutely nothing wrong with threatening to bring utter destruction on an enemy even if you don't intend to see it through.
Nor would I lose one second of sleep because of a threat to the Iranians. I simply don't care. For that matter, what was the actual harm/damage caused by the threat? What damage did it do that justifies removal from office? That's just absurd.