That's no excuse gay or not you should have said something at the time of it happening, I hate people who do this, I always park out of the way if I can and you can guarantee when you come back some one has parked there rust bucket next to your pride and joy, I always watch the person get in/out of there car when I'm parked in a bay with someone beside me.
Has it definitely chipped the paint? Have you given it a quick polish to see if its just paint from his door sat on the top of yours? I'm sure a mobile chip company would get rid of it no problem as it doesn't look very big.