It would've been a good opportunity to wake the player up a bit, since RPG protagonists always tend to meddle with shit that isn't any of their business. You know, underlining the fact that things would've been so much better if you just didn't do anything.
Naw, the option of disarming the nuke is pretty much the status quo. Keep in mind, as you set out, you know the nuke that the Monks have is fake already. So as it stands, nobody has the nuke, the monks are losing men faster than they can get new ones, and the situation is slowly, or maybe not so slowly, deteriorating anyway. Personally, I figured that in such a situation, the DBM would come out on top anyway, since none of the actions you would have taken there would have worked against their plan.
I would suppose Tigranes is referring to the 'you suck!' line and not the outcome itself, in which case he is absolutely right.
Seems right to me. A silver-tongued snake left at a loss for words as he lays dying in the dirt and his cult crumbles around him.