Mother Inferior: Diane Keaton?s weak performance sinks Because I Said So.

A movie is at a certain disadvantage when you want to punch its main character in the face: Because I Said So is, give or take, a torturous 102 minutes, thanks to Diane Keaton’s irritating portrayal of an overprotective mom. It’s not entirely Keaton’s fault, though considering her similar role in 2005’s The Family Stone, she’s not on a good track. Stepmom scripters Karen Leigh Hopkins and Jessie Nelson went delirious inventing Daphne (Keaton), an unbelievable nightmare of a woman who gives her youngest daughter, Milly (Mandy Moore), advice about her standards in men by saying, “Don’t forget that you have one breast smaller than the other.” Milly, you see, is “headed toward a cliff” because she’s in her mid-20s and isn’t in a serious relationship, unlike her married older sisters, Maggie (Lauren Graham) and—ughÔªø—Mae (Piper Perabo). So mother, thinking she knows best, takes out a personal ad on behalf of Milly and interviews the candidates, deciding that successful, by-the-books charmer Jason (Tom Everett Scott) is a terrific choice, while charismatic guitarist Johnny (Gabriel Macht) might as well be a serial killer. Milly meets both—and guess which one she likes better? Moore and Graham provide the only tolerable moments in Because I Said So, with director Michael Lehmann (who helmed the also-atrocious 40 Days and 40 Nights) allowing the actresses to add some bite to their otherwise good-girl characters. Perabo, meanwhile, barely registers in a role that exists only to round out the family. Perhaps Keaton was trying to make up for this lack of presence: She flounders, wails, and whines as the basket case who can’t handle following GPS directions and who conference-calls her daughters to check in on Milly when she’s on a date. (On the other hand, her frowny-face scene in which she asks her youngest what an orgasm feels like is absurd, too.) A cute dog, a cute kid, pretty speeches, and other romantic-comedy clichés only add to the mess, which will test your patience way before it comes close to touching your heart.