It’s less that he finds an argument whose premise is repugnant, and more that he realizes that he doesn’t have a good angle of attack for convincing the slavers to not mutilate/kill him at all, but does have one for delaying doing so. I’d argue it’s more of a “perfect is the enemy of the good” judgement on his part than a disagreeable argument (After all, Tyrion has gleefully made that clarification to several people before.)
It’s less that he finds an argument whose premise is repugnant, and more that he realizes that he doesn’t have a good angle of attack for convincing the slavers to not mutilate/kill him at all, but does have one for delaying doing so. I’d argue it’s more of a “perfect is the enemy of the good” judgement on his part than a disagreeable argument (After all, Tyrion has gleefully made that clarification to several people before.)