What the hell has gotten into David Mamet? The puzzlement is genuine, and the profanity is the cooing of a dove compared to the bad words Mr. Mamet unleashes in “Romance,” his outrageous new comedy at the Atlantic.

Let us take stock. Mr. Mamet, one of the great American playwrights, is now entering his fourth decade on the stage. At a comparable point, Eugene O’Neill had a few more successful works up his sleeve, weighty dramas of substance, but Tennessee Williams and Arthur Miller were both in decline. Mr. Mamet still shows the pugnacity of youth. Having demonstrated that he can do just about anything, he now unburdens himself of what may be his oddest something to date.

“Romance” is a willfully slight, happily offensive courtroom farce. Its targets include Jews, gentiles, homosexuals, Arabs, jurists, chiropractors, and allergy sufferers. The play is about as socially redemptive as a stink bomb, and 10 times as funny; I recommend it very highly.

I once saw a postcard of Mr. Mamet. He was seated behind a desk. There was nothing on the desk, and the wooden wall behind him was bare. There were, however, two windows, which framed Mr. Mamet as he peered at the camera. At first glance, the image looked severe and menacing, the portraitist’s equivalent of head-butt. But unless I’m mistaken (and I may be mistaken – I haven’t seen the photo in years), on one of the window sills, in the corner of the frame, leaned what I remember looking like a juggler’s club. This toy, this emblem of fun, turned the photo’s seriousness into a bone-dry prank. And that twinkle in Mr. Mamet’s eye? That means the prank is on you.

Mr. Mamet and director Neil Pepe play the same sort of trick at the Atlantic. Robert Brill’s courtroom scenery is a marvel of geometry: all right angles and grown-up furniture. (There’s also no music – the production could hardly be more spare.) A portrait of George Washington hangs at center stage. As events beneath him begin to spin out of control, his serene gaze begins to look positively ridiculous.

The defendant (Steven Goldstein) is on the stand, being grilled by the prosecutor (Bob Balaban). Like so much in this play, the particulars aren’t clear. (Most of the characters don’t even have names, just titles.) The testimony is carried out in Mametspeak, as is an interjection by the judge (Larry Bryggman), who wishes to note that Israeli and Palestinian leaders have come to the city for a long-awaited peace conference. Here is how he describes a parade welcoming them:

On our way to work today. The faces. Lining the streets. Perhaps you saw them? This man or that woman. Enemies, perhaps, certainly no more than strangers. Reaching out. Because of our Visitors. Yes. Yes. We have strife. But, but, their presence here. … I’m sorry, did I take my pill?

He did take his pill, the burly bailiff (Steven Hawley) assures him, but it makes no difference. Mr. Bryggman will go on popping them. I don’t know what he’s been prescribed, but to judge by the effects, it’s potent. Before long, he looks, and sounds, like somebody long overdue for rehab.

The judge has already started to unravel when the action shifts to an attorney/client conference. Here the real antisocial fireworks begin. The defense attorney (Christopher Evan Welch) lets slip a slur to his Jewish client, and away we go. The expected melodies are played – sodomizing pedophile priests, blood libel – along with some colorful grace notes of Mr. Mamet’s own invention.

Our intolerance tour next takes us to the prosecutor’s apartment, which he shares with his preening himbo boyfriend Bernard (Keith Nobbs).The play’s homophobic jokes, likes its racist ones, come wrapped in great swirls of profanity. As the prosecutor and his boy toy shriek at each other, we learn that homosexuals are vain, high-maintenance, and bitchy. Mr. Mamet’s comic assaults on queer stereotypes aren’t quite as sharp as the abuse for Jews and Christians. Still, in both cases you get the sense he has been building up a store of anti-PC vitriol for a long, long time.

When the trial reconvenes, Mr. Mamet produces some of his most inspired comic writing in years. A doctor (Jim Frangione) tries to mellow out the judge. In what is fast becoming a standard post-PC motif, the characters lower their voices when mentioning Arabs, unless they are saying nice things, in which case they speak loud enough to make sure everyone in the building can hear. I do not recommend this show if you are a gentle sort of person, who holds things sacred.

Screeching ad hominem attacks sometimes give way to physical comedy, which gives way to Gilbert & Sullivan-style topsy-turvydom. Many of the pratfalls belong to Mr. Nobbs, whose talents lay elsewhere. But nearly every time the comedy threatens to dry up, Mr. Bryggman or Mr. Welch – two of the canniest, most savagely funny actors in New York – deliver some perfectly timed bit of nonsense.

To what end does Mr. Mamet, august and gifted playwright, force his characters to say such many mean and dirty things? He seems to want the whole madcap business in the courtroom to echo the peace conference across town – to show, maybe, why peace always proves difficult – but a precise connection never becomes clear. If he lets his funny, foulmouthed characters give offense to teach us the value of x, or warn us of the dangers of y, or mount a high-minded attack on z, I missed it. (In my defense, I was busy laughing myself silly.) Whatever the intended point, Mr. Mamet must have known that shattering so many taboos would make us squirm, and laugh all the harder. The joke’s on us, but it’s a good one.

Until April 17 (336 W. 20th Street, between Eighth and Ninth Avenues, 212-239-6200).