The first time Matthew McConaughey appears onscreen in Dallas Buyers Club—that is, after he's shown thrusting away at two female rodeo groupies in the shadows of a backstage stall—the reflex is to gasp. That carved-from-amber beach bod, to which we've grown so accustomed, has been whittled down to a toothpick. He looks gaunt, almost insectoid, with a head too big for his neck and skin stretched like plastic wrap around his eyes and Adam's apple, a thick mustache as his antennae.   

It's a transformation mirroring that of McConaughey's career over the past year, ever since the day he woke up, put on a shirt and decided to become the best actor of his generation: The rom-com lothario, with the increasingly self-parodic public image, has withered away. In his place arrives a performer at his peak, in a role that better damn well win him an Oscar, as an AIDS activist the movies have never seen before: a shit-kicking, homophobic redneck. 

That redneck actually existed, too. In 1985, Ron Woodroof, a Dallas electrician, bull rider and pussy-chasing, coke-snorting degenerate, became one of the rare straight men in the early years of the AIDS epidemic to contract HIV. Left out of the trials of an experimental new drug, and frustrated by the grinding inertia of Big Pharma, Woodroof went to Mexico, where, with a cocktail of natural supplements and non-FDA-approved meds prescribed by a de-licensed American doctor, he was nursed back to health. Or, at least, made healthy enough to reinvigorate his instincts as a natural-born hustler: Figuring there was a great racket in AIDS drugs that actually worked, he returned to Texas and opened a "buyers club." Operating out of a fleabag motel, he skirted federal regulations by selling "memberships" at a rate of $400 per month and doling out the banned substances for "free."

McConaughey lost more than 30 pounds to play Woodroof, who's deathly ill when the movie begins, but it isn't some Method stunt: His survival mechanism is to throw around what little weight he has left, and the dissonance between his frail figure and intense narcissism gives the role its punch. He's an antihero in the truest sense, an accidental advocate you're not sure it's totally OK to cheer for. Told he has about a month to live, Woodroof proclaims he's not "a faggot" and declares, "There ain't nothing out there that can kill Ron Woodroof in 30 days." You cringe, but at the same time, who can root against that resolve?

To the credit of writers Craig Borten and Melisa Wallack and director Jean-Marc Vallée (whose next project is adapting Portlander Cheryl Strayed's Wild), Dallas Buyers Club never betrays the man Woodroof actually was. There are no weepy epiphanies, no soliloquies about newfound understanding. His business arrangement with a transgender woman named Rayon (Jared Leto, also emaciated, also fantastic) grows beyond a relationship of convenience, but it's never made obvious. A scene in which Woodroof physically forces one of his old chaw-chewing rodeo buddies to shake Rayon's hand isn't really an indication that his ordeal has made him any less of a dirtbag. It is, as with everything he does, about himself, an act of lashing out at those who abandoned him to die alongside a bunch of queers. In this film, the fact that Woodroof would deign to set foot inside a gay bar in order to rope in more members counts as a victory for tolerance. 

Woodroof enters the film an asshole, and he's an asshole when it ends. But McConaughey has played enough Texas good ol' boys that a gleam of Southern charm never leaves his eyes, even when inhabiting the slimiest of characters. In Dallas Buyers Club, that charisma doesn't just anchor the film but shocks it full of life. This isn't another movie about the heartbreaking destruction of AIDS—it's about the sheer human drive to stay alive in its wake. McConaughey, smartly, never makes Woodroof likable, because he knows that's not the point of his life, which continued for seven more years after his diagnosis. He may have been an asshole, but he was an asshole whose instinct for self-preservation eventually helped extend the lives of millions of better people. And, in the face of a plague, that's worth more than one jerk's enlightenment. 

Critic's Grade: A

SEE IT: Dallas Buyers Club is rated R. It opens Friday at Fox Tower.