Seems like all this trouble and risk could have been avoided by simply leaving a note on the car with a warning about cameras/police. That's going to discourage most people who think they are 'getting away with it' to stop.
Most likely saying "thank you for your comment" to this guy and eventually telling him "I am not interested sorry", would lost his interest. The story also stinks frankly. It starts off with my sister got some writing on her dirty car so she wasn't thinking anything and just wash them off. Next thing we see are the photos of that writing.. OR she wrote it herself for the story-telling?? highly doubtful. Then the guy is a dude and has crash on girl even tho the writing supposed to offend her because she's lesbian..? that's even harder to believe.
There has been so many fake stories coming out online these days just to catch few clicks that you cannot trust anything anymore.