Alternately bland, infuriating and witless, "Because I Said So" is a thoroughly unctuous romantic comedy that sends out the wrongheaded message that a woman's life is utterly worthless if she does not have a man to complete her. That the film was directed by a man, Michael Lehmann (2002's "40 Days and 40 Nights"), somewhat unsurprisingly suggests that there is a bit of a sexist attitude in what has been conceived. That the same movie was written by two women, Karen Leigh Hopkins (1998's "Stepmom") and Jessie Nelson (2001's "I Am Sam"), is simply inexcusable.

Longtime single woman Daphne (Diane Keaton) is fast approaching her milestone sixtieth birthday, and in place of seeking out a relationship of her own, she opts to secretly play matchmaker for her unlucky-in-love youngest daughter Milly (Mandy Moore). Setting up a personals ads on the Internet, she finds a conceivable winner in successful and wealthy architect Jason (Tom Everett Scott). As Jason orchestrates a meet-cute with Milly and begins to date her, Milly simultaneously starts dating handsome musician Johnny (Gabriel Macht), whom Daphne is less than fond of. As romances based solely on lies and deceit always must, Milly is forced to come clean to her beaus, one whom is hiding something of his own and the other whom feels betrayed. Seeing the mess she has wrought, it is time for Daphne to take a step back and recognize that it is no longer her place to meddle in her grown daughter's life.

"Because I Said So" is birdbrained hooey with the mentality—just barely—of a middle schooler. The premise, in which a smothering mother goes behind her daughter's back to find a suitor for her, is immature and shallow. Daphne speaks time and again about how critical it is that Milly win over a man "before it's too late," but Milly can't be any older than in her mid-twenties and seems fairly well put-together without one. Nevertheless, once Milly embarks on dual relationships with Jason and Johnny—a choice that is never justified with a reason—she instantly comes off as a careless slut who doesn't deserve a guy, period. Until her deception is uncovered, Milly never appears to have any trouble sleeping with both of them, considering marriage and children with either one, and not once feeling guilt over her dishonesty.

If the plotting is acutely flawed, the mugging, cookie-cutter filmmaking is just as problematic. This is the kind of movie where, during a love scene, a dog's reactions get more screen time than the humans. Earlier on, it should be noted, said dog humps a foot rest after seeing a pornographic video on the Internet. This is also the kind of film where practically every other scene, no matter the circumstances, must be punctuated with a cake falling on the ground or smashing into a person's face, or a wine glass or plate crashing to the floor. This is the kind of picture where there are not one, but two, group singing scenes between mother and daughters. And, finally, no dumbed-down waste of a love story would be complete without a climactic chorus of colorful onlookers who deliver one-liners at just the right moment and egg on the couple to get together. If this is all it takes to get a screenplay sold in Hollywood, my 84-year-old grandmother ought to start writing; she would be able to create something with more originality than "Because I Said So" could only imagine having.

As far as singer-turned-actors go, Mandy Moore (2006's "American Dreamz") has proven herself to be one of the most naturally talented. Not just a flavor of the week, Moore has a rich soulfulness to her voice and a vibrant charisma and range to her performances. It isn't her fault, then, that she is stuck playing an unsavory heroine whose mistakes, at least in the eyes of the faithful Johnny, should be unforgivable. Moore gives it her all, but her role is hopelessly written. As mother Daphne, Diane Keaton (2005's "The Family Stone") is humorous in highly sporadic spots, but mostly just overbearingly shrill. Daphne's motivations in butting into Milly's life are flimsy at best, and Keaton overplays things in a failed attempt to make up for the script's downfalls.

Lauren Graham (2005's "The Pacifier") and Piper Perabo (2005's "The Cave") are wasted to the point of being non-entities as Daphne's married daughters, Maggie and Mae. Graham's Maggie is viewed in one late sequence as being a disgustingly irresponsible psychiatrist who doesn't give a care in the world to her patient's well-being and mental state, while Perabo doesn't even receive one distinguishing characteristic. Finally, Gabriel Macht (2004's "A Love Song for Bobby Long") is perhaps the only actor to play a sane character whose decisions and reactions make sense. As Johnny, Macht brings some endearing shades to a part that amounts to being a love interest and not much more.

For a filmmaker who once directed 1989's mercilessly brilliant high school satire, "Heathers," it is depressing to witness where Michael Lehmann's career has taken him. "Because I Said So" screams of a work-for-hire gig, and Lehmann's handling of the project is spineless, threadbare and wholly inconsequential. The romance(s) are one-dimensional, the mother-daughter relationship is carried out like nails on a chalkboard, the humor is strained and too cute by a half, and the so-called dramatic monologues that pop up every once in a while clang with artificiality. The only good use for "Because I Said So" would be as a step-by-step handbook on how not to make a romantic comedy.