Who knows what those fruit cakes will do? To the extent I can figure out their psychology, I guess they wanted to "erase" the symbolism, of your having something nice, that they don't. In any event, it's a good thing they didn't take a screwdriver to pry the thing off, and if it was about time for replacement, then it's a little easier to take. The punks may return to the neighborhood, so take precautions (where you park, stuff that's visible in the interior of the car), and report it to the police. Perhaps a bit laughable, but then again the little things can tip them off to other stuff and suspicious behaviors.