An incredibly shrill comedy about the problems that erupt at a wedding between families of very dissimilar backgrounds, “Jumping the Broom” may get a pass from some because it gives major roles to talented African-American performers. That would be a terrible mistake. This would be an unpleasant, mean-spirited movie whatever the skin color of the feuding folk, and despite its tacked-on happing ending.

The couple are lawyer Sabrina Watson (Paula Patton), a young woman from a wealthy family tired of one-night stands who meets the perfect man—handsome, charming Wall Street broker Jason Taylor (Laz Alonso)—and is soon engaged to him. But there are storm clouds on the horizon. Sabrina’s mother (Angela Bassett) is rather a snob concerned that her husband is having an affair with his secretary. And Jason’s mom Pam (Loretta Devine) is a short-tempered, intense Brooklyn postal clerk already nonplussed because her baby hasn’t introduced her to the bride-to-be and primed to butt horns when she arrives for the ceremony at the Watsons’ palatial Martha’s Vinyard estate.

One presumes that the infighting that quickly breaks out between the two mother-in-laws-to-be is intended to be humorous, though edgy. But it’s so crudely written and broadly played that it engenders queasiness rather than laughs. It’s not just that Pam’s attitude toward her prospective in-laws is rude, obnoxious and, when it comes to a Watson family secret that she’s willing to use for her own purposes, emotionally destructive. It’s that her desire to continue controlling her son’s life is rather ugly, too. It’s a pity that Devine, an amazingly talented actress, is stuck with such a role—which, by playing honestly at full force, she actually makes even more unlikable.

The other major characters are poorly drawn, too—Sabrina, it turns out, is only marginally less snooty than her mother, while Jason is such a weak-kneed pawn in his mother’s hands that he comes across as spineless. There are fleeting moments of fun from the supporting cast, including Tasha Smith as Pam’s chum, Mike Epps as her worldly brother-in-law, and Gary Dourdan as a chef with a libido. But they can’t make you forget the sourness at the center of the movie. The happy ending that finishes things off will strike you as both unconvincing and undeserved.

Still, it must be said that “Jumping the Broom”—the title comes from the practice slaves used to indicate their marital commitment at a time when regular ceremonies weren’t allowed them, which of course Pam wants included in the service while the others do not—looks good, with cinematographer Anastas Michos making good use of the lovely waterfront location. But the surface elegance somehow only makes the underlying nastiness more noticeable.

The picture comes from the production company of Dallas preacher T.D. Jakes, who also appears briefly as the Watson’s minister, who will oversee the service. His acting is more natural than in his previous films, but though it’s clear that he’s interesting in exploring tensions that exist within the African-American community, it isn’t apparent the message he’s trying to get across here, unless it’s that families shouldn’t judge one another on the basis of economic and social differences. If that’s all there is to “Jumping the Broom,” it isn’t enough.