OK so I came up with a slightly crazy idea. Do you know how cars are emblazoned with logos and emblems? Like the brand name (Toyota), the car name (Kluger), engine and other doodads (V6 etc etc). What if we made like jokey versions of these to replace on our cars? Like make a Toyota logo but it looks a bit more like a penis.
Instead of car doodads we just make up acronyms with no explanation (AR-X, BFI, MIG-TL). We could also have unfortunate acronyms with explanatory text below it, like "AIDS" and then in smaller text it would say "Advanced Infra-red Drive System".
If enough people do it to their cars then it will show that we don't respect them.
I've always thought it would be fun to print out a bunch of stickers with sayings like, "I suck a driving," and slap them on shitty drivers cars. The main opportunity I see for this is when you are trying to cross the street and a car is pulled up in the sidewalk, forcing you to have to walk behind their car. As you are passing you could slap a sticker on their trunk. I think it would be a funny thought of them to find that later and realize they have been driving around all day or week with that thing.