A forthcoming documentary focuses on anti-graffiti zealots who commit the same crimes they crusade against. In “Vigilante Vigilante,” San Francisco filmmakers Max Good and Nathan Wollman successfully stalk and unmask a local man, known as the “Silver Buff,” who “surreptitiously spray paints metallic silver blobs over existing graffiti, almost always doing more damage than was there to begin with.” Along the way, the filmmakers also profile other prolific graffiti-hating vandals including New Orleans’ “Gray Ghost,” Fred Radtke, who was recently busted for vandalizing a legal mural and ordered to get permission to paint on other people’s property. Watch a preview from “the battle for expression” after the jump.