Oh, I expect he knew exactly what he was saying

A lot of these folks count on consumers not knowing their rights and not knowing their options. They use fear to drive the reaction they want to see. The moment the consumer speaks up and says “I already know you have no legal authority to do this”, the game is over. I wouldn’t even get into the amount of the bill, how they found you after all these years, any of it. Just tell them you already know they have no legal authority to pursue payment of this bill, and if they continue to try, you’ll press charges, which DO have authority.