Though the title “Machine Gun Preacher” (as well as the movie’s lurid poster) might suggest a grindhouse exploitation movie from Tarantino or Rodriguez, Marc Forster’s film is actually more like one of Ed Zwick’s preachy pictures on important subjects. It stars Gerard Butler as a born-again Hell’s Angels type who, during a missionary trip to Sudan, is so moved by the brutalization of innocents he encounters there that he establishes a sanctuary for the youngsters who are often kidnapped to become child soldiers. But he also takes to using force against the vicious thugs who destroy whole villages in their campaigns and compel boys to join their ranks.

One can imagine a powerful film being made of this story, centered on the question whether Bibles and bullets should ever mix. But though this tale of redemption and struggle invites consideration of their compatibility, Forster totally sidesteps the issue in favor of a treatment that essentially just presumes the moral appropriateness of a man of God taking up automatic weapons to deal with evildoers. That may be because it’s based on the life of a real person—Sam Childers, whose autobiographical book “Another Man’s War” inspired Jason Keller’s script. But while the film, like the book, hardly paints Childers as some sort of plaster saint, it utterly fails to address the very matter that could have made it provocative and challenging.

What we’re left with instead is a confused, unsatisfying portrait of man rescued from vice by religious conversion who dedicates his life to saving children from abuse by any means necessary. Butler works very hard in the lead, bellowing through the early scenes of his unreformed days of boozing and drug-using that culminate when, believing that he’s killed a man, he finally gives in to his wife Lynn’s prodding to accept Christ and agrees to be baptized. It apparently never occurs to him, one might note, that coming to terms with God and being forgiven might involve confessing to his crime and accepting responsibility for it. But at least he gives up alcohol and pharmaceuticals to become a hard-working guy in the construction business.

Responding to a call from a visiting missionary, Sam travels to a mission in Uganda, but is drawn to investigate the situation in nearby southern Sudan, where the brutal Lord’s Resistance Army is engaged in its campaign of mindless terror. Deeply affected by what he experiences there, he determines to devote his life—and his family’s resources—to save as many children as he can from the devastation of the LRA. What begins as a mission becomes an obsession as Childers’ drive to raise funds back home becomes so fanatical that people’s failure to respond with as much zealotry as he possesses drives him into a rage. So does the ineffectuality of anyone in dealing with the LRA, which leads him to take up arms against them himself.

Had “Machine Gun Preacher” dared to address the conflict between a religious calling and responding to violence with violence—even if Childers himself never felt it—it could have become a compelling “issues” film. But it doesn’t. It’s content instead to be just another uplifting story about an idealistic (and in this case, religiously motivated) outsider—a white one, of course—who becomes a savior to people in the Third World. Butler certainly brings energy and intensity to his portrayal, making Childers something more than a mere symbol, but those whom he helps remain virtual props, whether they be the army officer who becomes his ally or the scarred young boy rescued from the carnage who remains mute until it’s time for him to deliver a poignant speech to an exhausted Childers near the close. (There is one grimly powerful scene of a woman terribly injured by the LRA for talking back to them, but the other scenes of atrocities are more gingerly handled.)

In support Michelle Monaghan radiates strength and concern as Childers’ wife, and Madeline Carroll has a few good moments as the teen daughter who feels so neglected by her father that she accuses him of loving his African charges more than her. No one else makes much of an impression except for Michael Shannon, who’s typically edgy and nervous as Sam’s old partner in crime, whom he rescues from a self-destructive tailspin but ultimately abandons, with devastating results. The picture plays his death for tearjerker effect but fails to deal with the ethical complexity surrounding it, insofar as Sam’s concerned.

And that, unfortunately is typical of “Machine Gun Preacher,” which remains a morally muddled tale that treats serious issues of faith and violence simplistically rather than with the subtlety they deserve. It’s certainly well-intentioned and decently made—Roberto Schaefer’s camerawork is solid, and in the action scenes in Africa better than that—but while it draws a warts-and-all portrait of Childers himself, it fails to deliver a nuanced, sophisticated view of his mission and methods.