The movies of John Waters have always been an acquired taste, and those who have been afflicted with it will probably enjoy “A Dirty Shame,” the writer-director’s latest attempt to be shockingly funny on the subject of sex. Unfortunately, though the picture is definitely about sex–indeed, it’s about nothing but the joy of freely giving in to every lustful impulse–it’s really neither very shocking nor particularly funny. In fact, it’s rather a bore–the sort of puerile smut that might pass muster in a high school locker room but seems woefully amateurish and crass on a theatre screen; one might be tempted to call it sophomoric, but that would be an unjust denigration of second-year students everywhere. The picture could work as a midnight movie if the audience is properly lubricated, but a sober viewer is unlikely to be much amused.

The script isn’t so much a story as a premise endlessly repeated. Sylvia Stickles (Tracey Ullman) is a straightlaced Baltimore housewife who’s changed into a raving sex addict by a bump on the head. This concerns her flaccid husband Vaughn (Chris Isaak) and enrages her old-fashioned mother Big Ethel (Suzanne Shepherd), who, together with neighbor Madge (Mink Stole) organizes a neighborhood group to enforce codes of decency. On the other side of the divide is a cultish auto mechanic called Ray-Ray Perkins (Johnny Knoxville), who leads a movement espousing a sort of defiant sexual anarchy, and enlists the altered Sylvia among his acolytes. Adding to the commotion is Sylvia’s daughter Caprice (Selma Blair), a looker who’s had her breasts augmented several times over to increase her career as an exotic dancer. Caprice has been put under house arrest for her conduct, but that doesn’t stop her biker fans from stopping by to ogle her. And a bump on the head changes her perspective, too.

There isn’t any point to disentangling what happens in “A Dirty Shame.” The so-called plot is just an excuse for a disorganized smattering of deliberately tasteless situations, crude gags, gross characterizations and double, triple and quadruple entendres, all vaguely related to the idea of a small-scale war between prudery and let-it-all-hang-out abandon. There’s certainly no doubt where Waters stands on the matter, and in itself that doesn’t matter much. Nor does the director’s customary lack of style, with its lovingly clumsy attempt to recreate a 1950s ambience and to emphasize garish color schemes. What does matter is that it’s crushingly unfunny, the bits coming across more as repulsive than as daringly risque. And Waters’ direction is both incapable of employing the undoubted talent of good actors like Ullman or of extracting even a glimmer of it from the likes of Isaak, Knoxville or Shepherd, who are either so pallid as to virtually disappear into the woodwork (Isaak), or so loud and blaring as to be gratingly exhausting (Knoxville and Shepherd). As for Blair, she seems so concerned with simply maintaining her balance with those enormous hooters that she can’t give her attention to much else.

There are some out there who will embrace “A Dirty Shame” as a return to Waters’ gleefully tasteless early movies. But the sad fact about this tedious bit of one-joke sloppiness is that it isn’t really dirty enough, except in the most juvenile way, and it’s shamefully unfunny. John Waters may rejoice in never having grown up, but his bad-boy exercises in unfettered libido have never seemed less appetizing than they do here.