Michael Moore's a funny guy, but damn, can he be depressing. The corporate watchdog and guerrilla filmmaker has turned activism into a comedic art form, attacking General Motors boss Roger Smith in Roger & Me and Nike's Phil Knight in The Big One. But his latest, Bowling for Columbine, takes on much darker subject matter: gun violence and murder in America, specifically the 1999 Columbine High School shootings in Littleton, Colo.

Roger & Me was hilarious, but Bowling, though it benefits from Moore's overgrown-muppet persona, isn't the kind of film you'd want to watch again and again. It's an incredibly effective piece of journalism mixed with liberal dogma that leaves you feeling squashed and helpless--and ready to move to Canada.

Columbine didn't occur in a vacuum. In the U.K., an average of 68 people die each year from shooting deaths; in Japan, it's up to 139. But in the United States, guns kill 11,127 people a year. Why so many? Moore decides to find out.

It must be, he figures, because of the huge number of guns available in this country, right? Wrong. Canada, as Moore discovers, has at least as many household guns per capita as we do, but a mere fraction of the number of deaths.

Well, then it must be because of our aggression-packed movies and entertainment--Terminator, Mortal Kombat, Marilyn Manson. Nope, sorry, wrong again. Most video games come from Japan, and bloody American action movies are shown in theaters all over the world. Yes, they watch and listen to the same crap in other countries as we do here.

OK then, it must be America's violent history. But wait, what about Germany? What about Japan? And jolly old England--wasn't there something about an empire...? America may be the most conspicuous international bully, but it's certainly not the first. In the film's most overtly manipulative moment, Moore shows a montage of scenes of war crimes and international oppression, set to Louis Armstrong's "What a Wonderful World."

Perhaps, then, we can blame gun violence on what NRA honcho Charlton Heston mumblingly refers to as this country's excess of "mixed ethnicity." (Moore uses his lifelong NRA membership to score an interview with the Alzheimer's-afflicted star, confronting him about the NRA's vile tendency to hold rallies in places just days after school shootings.) How convenient: It's the black people killing everyone, yeah, that's the ticket--why else would our prisons be filling up with African-American men at such alarming rates? The "urban" community must be the problem.

But no. Moore interviews several law-enforcement authorities, and all of them--surprise, surprise--say the problems they've had with guns in schools have invariably come from white, suburban neighborhoods.

OK, so if it's not "mixed ethnicity," just what causes this glorious country, Leader of the Free World, to have 100 times as many gun-related deaths as anyone else in the free world? It's a puzzle so damnably complex it makes you want to blow somebody's head off. We might never know the answer, but Moore makes a good case for part of the blame resting on the media and the culture of fear it promotes.

TV news has become a graphic-heavy pastiche of lost kittens and violent crimes, with a healthy dose of useful information along the lines of "the suspect was a black male in his 30s." Moore quotes statistics showing that, in a period when murders actually decreased by 20 percent, media coverage of murder increased by 600 percent. An ingeniously warped cartoon segment by South Park creators Matt Stone (who attended Columbine) and Trey Parker fast-forwards through the history of white America as it was shaped by fear--of the British, of the Indians and most tenaciously, of black people. Marilyn Manson comes off as the voice of reason, discussing television's self-sustaining pattern of creating fear to sell products: If you have zits, girls won't like you, so buy this zit cream; if you have nice things, someone will steal them, so buy this security system. The media feeds us fear, and the corporations sell us the tokens to ease it.

Still, no matter how effective his documentaries are, Moore is inevitably preaching to the converted. Maybe he should give away free handguns with each ticket to attract those who really need to see this film.

Bowling for Columbine

Rated R Opens Friday, Oct. 25. Fox Tower.