I would have told agent #2 to go @#$% himself, and possibly members of his family too.

Since neither of these idiots have power of detention, I would have invited them to meet me at the gate of my departing flight with any law enforcement personnel they saw fit to bring. I am quite sure that would have ended any further discussion.

Had they attempted to illegally detain me, it would have been a mental coin flip between "go time" and filing a lawsuit.