I'm not sure about other people, but I feel that when I drive my vehicle I have a right to attach the decals and stickers that I desire to it. My desired form of automobile advertising usually stays along the lines of college decals, flags, and a single statement of rebellion: “I Love Jet Noise.“
My current issue is with the fact that most automobile dealerships in the United States fasten small placards, license plate frames, or stickers to the rear of your vehicle. They presume they have a right to do this even when you specifically ask them not to. I have even had a service manager cheerfully inform me that the dealership emblem had “fallen off” and asked if I wished them to replace it. He seemed surprised, even shocked, when I informed him that it had not fallen off. I had removed it.
I had violated an unwritten rule that you should never question the dealerships' right to attach their name to your new vehicle. Those attachments on my vehicle are free advertising. I would consider retaining them if the dealership paid me an annual fee to display them. That seems fair.