This happened to me ages ago in my previous white E46 BMW 323i, I was sitting in the car with my GF and her mate eating maccas (Hallam, Princes hwy) after a big night out. The kids in the next parking spot had a full car load of drunks.. one in the back left seat opened the door and knocked my rear right door.. as soon as I heard the knock, I got out the car grabbed the kid and asked him WTF his problem was, has he no respect etc.. as soon as I grabbed him, he started tearing up, my GF stopped me, he then jumped back in the car, they then sped off. There was only a tiny nick, so I polished it out and came up fine.. The reason I acted the way I did is because previously I parked at a club (Motel, city rd, south Melbourne) some d*** head had jumped on my hood, ruining it! I'm over idiots who are either jealous or simply don't care! I now park far away from other cars in open, well-lit areas and haven't had an issue in 5 or so years :)