Attempted assault on Kingston Hill

The way I see it, slashing his tyres and smashing his windows would be criminal damage, whereas writing the word "CUNT" several times on his car in brake fluid would just be expressing your personal opinion.

Mind you, I haven't got any legal training.

Do nothing that could be construed as damaging.

Sticking something to his car windscreen cannot possibly be construed as damaging- witness parking wardens sticking tickets to windscreens all over the country day after day.

This would be non-destructive, therefore not leaving you open to any claim for criminal damage etc, and also if you used a suitably sticky glue for the sticker (maybe a sheet of Vinyl with you opinion spelt out on it?) it would seriously put a crimp in the owners day when it came time to jump in the car and offski.

Certainly if it happened more than once...