Few issues in America are as grossly politicized as marijuana legalization, with activists on both sides so intent on demonizing each other that there seems to be little hope for a pragmatic look at the drug and its effects, positive or negative. Fighting propaganda with propaganda, Ron Mann's smug, self-satisfied pro-pot documentary Grass only exacerbates the problem. Sketchy as history and even more dubious as cultural commentary, the film preaches to a toasted choir, taking potshots at hysterical archival footage while skimming through the shifts in government policy. Nevertheless, many of Mann's points are cogent and illuminating. As narrator and noted hemp advocate Woody Harrelson explains, conservative forces have long used marijuana laws as a tool of oppression, from the influx of Mexican laborers early in the century to alleged Communist subversives in the McCarthy era, to hippies in the late '60s. Over that time, the government has spent and continues to spend hundreds of billions of dollars enforcing harsh penalties on laws that have little basis in scientific fact. Mann's most effective touch is to show how the government changes tacks to suit the times, claiming at various points that marijuana will lead to addiction, insanity, murder, brain damage, dysfunction, and a segue into deadlier drugs. Some of the footage is admittedly hilarious, including early lab shots of toking chimps and a baked young test subject eager to further the scientific cause. But after a while, Mann's refusal to view the drug's opponents as anything but seething zealots or unenlightened nitwits speaks to a narrow-minded attitude that's just as suspect. If the decriminalization of marijuana is a reasonable idea, isn't it also reasonable to admit that smoking pot isn't always beneficial? Does Mann fail to notice the similarities between the bug-eyed teenagers in the camp classic Reefer Madness and the giant blunt Cheech & Chong smoke on the freeway in Up In Smoke? He damns the former as silly propaganda while celebrating the latter as an example of '70s permissiveness, but when both clips end with a car careening off the road, the distinction seems unclear. Grass ends with the urgent footnote that more marijuana-related arrests have occurred during the Clinton administration than at any other time in history. That's a problem, but if Mann's obnoxious documentary is any indication, the level of discourse needs to improve significantly before it can be solved.