Calling a course of action "inconceivable" in the course of analysing it is the same rhetorical device as saying "not to mention" right before mentioning something.
Yes, 14 years ago, in the middle of a spectacularly successful debellatio of Saddam's army, and with every prospect of clear sailing for more than half a million troops all the way to Kurdistan if we had wanted, invading and occupying Iraq was deemed "inconceivable" in that same rhetorical sense.
When you work with emotionally disturbed adolescents and the first words out of a new patients mouth are "I'm not gonna hurt you", the feeling you get is not reassurance.
Giovanni