Actually, I put stickers on both my cars. I did not have any problem, but I was very nervous about it. Someone tore off one of the stickers, but that's as bad as it got.
You're lucky. When I moved to Wisconsin, my car had an old Bush/ Quayle sticker on it. The 'toon had won the election even & my car got keyed. And I know it was the bumper sticker that triggered it because the sticker had been keyed rather maliciously also.