Max Good's film quickly sketches – you could say "tags" – the history of graffiti in America, rousingly in favor of even the scribbliest scrawl as a mark of self-expression in a repressive society. His true focus, however, is not on valorized spray-can outlaws but instead on a counterforce of self-appointed antigraffiti activists, roaming urban streets painting out every random mark they see. Good tracks down three of them, all of them more or less angry, more or less lone middle-aged white men, devoting most of their imaginative lives to splooshing nullities of gray or silver paint across city horizons. Thus their nicknames: "Grey Ghost," "Silver Buff." Good is good at catching out these hitherto anonymous men in New Orleans, L.A., and Berkeley, and although he evidently hates what they do, their DIY spirit mellows even him, and by the end of this worthy film he allows them a grudging respect. Along the way, pro and con debates on the faith of graffiti get a fair hearing; you have to admire an advocate of outsider art who leaves in footage of an antigraffiti resident leaning in to gouge scratches on the camera lens, claiming to be an outsider artist too.