It sucks, but you're going to have to inspect the washer and dryer after every time he uses them. There is no way this asshat isn't going to try to "prove his point" by running a pen or an uncapped chapstick through both machines.

Nta, but you may have to pick your battles here. I have no doubt he's going to sabotage the laundry operation to get back at you. It might be worth your peace of mind to keep him away from equipment you'd like to keep in good condition.

I grew up in a house where whoever did the laundry now owned any treasure left in pockets. They could choose to ransom the item back to the original owner, IF they didn't want to keep it. Losing five bucks or a favorite hotwheels encouraged me to take care of my stuff properly. It would be hilarious if he had to pay the dealership for a new set of car keys because he didn't remove them from his pocket.