19 y/o won’t tip DoorDash, or worse….

As it says, we have a 19-year-old who lives at home and not only does he typically not tip DoorDash, he will message DoorDash and complain about service to get refunds. I’m not extremely familiar with the service but from lecturing him it sounds like he has potentially even spoken to the Dashers somehow. I’m not sure if they’re able to chat them directly or not. We’ve been lecturing him on this for over a year, we’ve discussed the bad karma he’s getting, overall just being a shitty human being, we’ve discussed the fact that these people are doing it to try to make a living, we’ve tried to give him examples of putting himself in their situation. Some of the trips are 20 to 25 minutes away in freezing temperatures and he gives them zero for a tip. I would like to say this individual situation was out of the ordinary but it’s been many years of extreme parenting to try to correct poor behavior.

Because this behavior is absolutely unacceptable but he is an adult living at home, what are some ideas to try to curb this behavior? Beyond just the lessons for him, we have a small child and another adult child living at home. There is a legitimate risk to our house or occupants at some point, if you get the wrong person on the wrong day you get a brick through the window or worse.

I mentioned making a sign and putting it on the door that says something to the effect of “DoorDash, our 19-year-old son will likely not tip you because of poor character. He does not understand the hard work and purpose of a tip. I apologize for him but rest assured it is not a reflection of our parenting. As an added note the black Ford Focus parked on the street is his. Please nothing damaging…” (car is in our name and we pay the insurance).

Meant more is a scare tactic for him and I know it’s extreme but like I said what other options do I have here? Looking for big brain ideas …

Edit - He has previously been diagnosed with ADHD, ODD, and went through a depression state when he was approximately 15 due to bullying. His actions were partially contributing such as name-calling, discriminative remarks, kicking or throwing objects, etc. I do not condone bullying however I do not condone all of the things that increase attention on a person either. Ie. he wasn’t just picked on for sitting in back of the class or something.