And later, if you keep going: "I told you to shut up. Look, either you're taking this joke way too far or you are literally insane. How am I supposed to believe anything you say now?"

You could always say something like "I believe X, but given your epistemic position, I understand your unwillingness to believe me." I would accept that from somebody who was ostensibly abducted by aliens.

ETA: added "ostensibly." =)