If Gary Busey ever played Elmer Gantry, he'd look like Reverend Billy, the real-life fire-and-brimstone preacher who, as the kooky star of this road documentary produced by Morgan Spurlock, embarks ''on a mission to save Christmas from overconsumption.'' The movie has a sharp point Americans shop too much but it's a problem that its bellowing hero, always accompanied by his red-robed Church of Stop Shopping Gospel Choir, is so off-putting; a crazy guy who wouldn't sound so crazy if he just didn't act so crazy. B-

