I haaate that. I had people do it to my rat rod ALLL the time, I had to explain to these people that the more sheet metal I have to fix the more time I will spend when I do restore the car. No one offered insurance info, nor would I have bothered with a claim.
With my nicer cars, I have been pretty blatant...
"Excuse me, does my car look like a good place to rest your ****ing door?"
I even took a cell phone pic of someone doing it at the grocery store before telling them they were a jerk... Closed their door and denied it... offered to show them the pic. Crazy Canadian people.