The slyest aspect about Lone Scherfig’s “The Riot Club” is also its most maddening one. Structurally, the whole production is a come-on, a tease, a manipulative stunt. It begins in lusciously ribald fashion as we are treated to nineteenth-century sexual shenanigans amid the upper classes at Oxford University: white wigs, splashy capes and all. A beloved hedonist is murdered after cuckolding an older man; to pay heed to his decadence, his peers vow to start a club devoted solely to campus debauchery.

Cut to present day: the titular group, though composed of only a handful of students, still wreaks havoc upon Oxford. The wigs are gone, but the poncy navy blue capes remain, as does the foppish, port-swilling tomfoolery, the glass-smashing rituals and the wanton seduction of willing co-eds. Effete, smug and unendingly rich, the club members’ worries are already over, for life. No matter how many uptight galas they violate, they will never be expelled, for their parents bankroll the school, and their antecedents’ portraits cover the walls of its art galleries. Two newly-enrolled students, Miles (Max Irons), a caddish yet basically decent young man, and Alistair (Sam Claflin), piercingly handsome yet socially awkward, are lured by the club and prove themselves fit for its strenuous hazing ritual.

Up until this point “Riot” is cheery, irreverent, even erotic fun. Miles’s slick courtship of the comely yet down-to-earth Lauren (played by an excellent Holliday Grainger) is alluring: there’s a remarkably frank and sensual tryst in a tony, bookshelf-lined office. Scherfig and screenwriter Laura Wade—adapting from her 2010 play “Posh”—are adept at making the audience feel the same longing as Miles and Alistair do to fit in to this secret society, obnoxious as it is. For awhile, it seems that “The Riot Club” will be a more boldly pro-fraternity film than “Animal House,” a sort of Lindsay Anderson’s “if…” in reverse: the protected, carefree establishment vs. the hard-working, financially stressed killjoys.

Then, like an anvil plunging through the beer keg, the movie nosedives into sorry, stale preachiness. The action moves to an ill-fated club dinner at—for reasons never quite explained—the backroom of a provincial countryside pub. The staginess of the initial content wins out, the editing becomes as dull as the monologues, and even the character development gets flabby. Alistair, jealous of the attention lavished upon Miles, suddenly loses all his charming gaucheness and becomes the group’s furious, bullying, Thatcherite leader. He’s sick of apologizing for being rich; what’s wrong, he says, with destructive behavior if his wallet can handle any damages?

This blunt character shift would be acceptable if the film handled Alistair’s potentially hilarious—and scathingly satiric—quandary with any humor, but it’s presented with drop-dead seriousness. Alistair even says things outright that the action could easily convey (“I’m sick of the fucking poor,” etc.) The blue-collar foils for the club are meek, one-note ciphers. And worse, the film’s pat, gutless denouement can’t begin to justify the brutality of its climactic event. “The Riot Club” means to lull and then lecture you, but its diatribes are painfully old hat.