If I see that happen to my car, I would ask what his opinions were about my work, and value his opinion. If it made sense I would take that into consideration and repair the bs i did to my car. If what ever he stuck on it was totally offensive or disrespectful or damaging to the car, it would be different. And if my car is in a show, it has a sign in the windows “look don’t touch” then there wouldn’t be an issue. Reason I do that is I am generally not hanging around my car, my examples I gave prior; dog, baby, gf, lawn… I would be present during the touching. lol My land has a no trespassing sign on it for a reason… just like my show car.