Geez, the way to deal with anything these days is video tape it, don't get physical.
On a bus, see a guy vandalizing it: video.
Someone keying or pissing on a car: video.
Then you've got evidence and can get the police after them, file a claim against them.
The exception is preventing someone from getting hurt - then go help.
Guy with Ferrrari is a douche-waffle. Videoing the prank wouldn't do him much good since he's already illegally parked and the guy wasn't actually pissing on the car.