If the license plate is deemed public property, then removing the piece of plastic from it is like removing chewing gum from a picnic table. It is not comparable to slashing tires, because slashing tires is vandalism, whereas removing an illegal modification from a license plate is the undoing of vandalism. (I don't know why you would compare any of these to a reckless act endangering multiple lives, like jumping in front of a speeding car.)