“Bad Santa” charts the end of what has apparently been a long, slow decline for one of Hollywood’s crassest heroes ever, Billy Bob Thornton’s disastrous Willie. As in “Ghost World” and “Crumb”, director Terry Zwigoff’s comics background has helped him craft an exceptionally subtle film. In comics the bounding boxes are always a reminder of the artist’s unwavering eye as he captures his grotesques in a series of little prisons. The neutrality inherent in the form gives the stories just the right ironic distance.

To help achieve this, Zwigoff uses wider shots to create visuals that come to seem like sequences of panels. There’s the wide shot of Willie stumbling into the alley, pausing, and nonchalantly vomiting. Later we’re given a panorama of Willie eating lunch in a mall, peeking out from half-closed eyelids at half-pretty women. The obvious joke is that his disheveled, sleazy figure is a stark contrast to the dull middlebrow stasis of the “food court”. Zwigoff goes further. He doesn’t merely show Willie in this environment, he plants him there, like a human landmine, to watch the conflict between man and mall—and it’s not clear which side is more odious to the other. (The same dynamic exists in “Ghost World”, where the geeks and the squares battle without Zwigoff taking sides.) Absurdity delivered in flat, even tones: that’s the feel of “Bad Santa”, and it’s one reason why this film is so much more than merely another gross-out comedy.

Zwigoff gives us Willie in all his mad, bottomed-out glory, but there’s a dose of sympathy in there, too. The character is a bastard, no doubt about it, yet the film never judges him. We are allowed to observe and enjoy him and the other wonderfully weird characters without the lame manipulations of either a feel-good underdog story or the “zany” comedies obsessed with sex and poop. Vulgarity is the subject, not the method. Another reason “Bad Santa” is such a winning movie is the simple fact that Willie’s scheme—playing Santa Claus to gain access to department stores so he can rob them—is merely an exaggerated version of the kinds of vexed ambitions most “respectable” people chase. If anything, Willie seems like the bleak alter ego of a Capra everyman, only later in the game, defeated and damaged in places too deep to fix.

Indeed, the juxtaposition of a slumping depressive in that cheerful red suit is a concrete manifestation of the fake persona most of us have had to adopt in the workplace at some time or another. Who hasn’t put on The Happy Mask? Billy Bob Thornton’s performance is as good as anything he’s done to date, and particularly brave because he works assiduously to make the character as unlikable as he was written. When The Kid serves him orange juice one morning, his alcohol-soaked brain seizes up for a moment. “Orange juice...? What’s in it?” he asks in a voice of suspicion, as if it were inconceivable that a non-alcoholic beverage should exist as anything but a mixer. It’s been that kind of life.

Few actors would have played it to the hilt as Thornton does here. He relishes the numerous opportunities for squalor and shabbiness afforded him by Glenn Ficarra and John Requa’s fine screenplay. Importantly, though, he imbues Willie not so much with cruelty as indifference. Willie isn't bad, he's just too lazy to do any good. Such is the tiny strain of dignity Thornton managed to give the character, gambling that Zwigoff’s evenhandedness would complete the hint—for it can be no more than a hint—that despite everything Willie might yet be redeemed.

The gamble pays off. “Bad Santa” dishes out two hours of moral turpitude, nonexistent hygeine, and a remarkable run of lying, cheating, and physical abuse. And by the end, against all odds, we’re rooting for Willie as if this actually were one of those sappy Christmas movies the film’s ostensibly mocking. Zwigoff presents human weakness without giving the audience the comfort of a settled perspective. He won’t let us condescend. He banishes smugness. More than that, it’s a humbling movie to watch, since it makes us wonder if maybe we have more in common with these low-lifes than we’d care to admit. There’s no better Christmas message than that.