"Maybe, but that would seem to make free speech a defense in any graffiti case."
You don't see a material difference between putting your name on an overpass, and writing criticism of a bank in front of that bank?
I'm not saying it's unreasonable to charge him with vandalism (though I don't think that's a slam-dunk either), I'm saying that the *reason he did it* matters, *especially* because that reason is constitutionally protected.