So, obviously it's a ridiculous charge. They shouldn't put that mural on a public road and if they do they absolutely shouldn't get upset about people using that road (or even making political statements since it's public property). That said, it's not a straight equivalence to say people don't get in trouble for burning an American flag. You can burn your own flag all you want, but if you go and burn someone else's American flag you will probably catch a charge.