One could be forgiven for assuming that John Krasinski plays the title character in “Angry Alan,” a briskly entertaining and deeply unsettling new play by Emily Skinner. The program features a photo of the actor, best known for his work in the NBC comedy series “The Office,” with his mouth open as if screaming, and his other handsome features clenched in a simulation — or perhaps a parody — of abject rage.

In fact, though, Mr. Krasinski, who is the only player onstage for most of this off-Broadway production, is cast as Roger, a middle-aged divorcee who, since losing a high-flying executive position at AT&T, has been reduced to managing the dairy department at a local Kroger. He’s also saddled with making child-support payments to his ex-wife, for a son he barely ever sees. “I haven’t felt good for a while. And I mean maybe years,” Roger concedes.

He is, in short, perfect bait for the actual Angry Alan, a fictional personality who is a prominent figure in what’s been called the “manosphere,” an assortment of online platforms rooted in the men’s rights movement that gained ground in response to second-wave feminism. In real life, its stars have included the likes of Andrew Tate, an entrepreneur who has been accused of rape and human trafficking, and Nick Fuentes, that reliable troll of many historically oppressed groups, who famously reacted to the overturning of Roe v. Wade with this charming one-liner: “Your body, my choice.”

Such egregious extremes did not materialize in a vacuum, any more than did Trumpian populism, with which they’ve been associated. Much has been written, not all of it by far-right activists, about how boys have languished academically as more and more focus has been placed on boosting the confidence and supporting the achievements of female students in particular. 

Then there’s the touchier issue of sexual assault and impropriety. “Believe women” became a rallying cry for the #MeToo movement, but false or distorted allegations, however rare, have had devastating consequences for both true victims and the unjustly accused. That’s to say nothing of men who, in recent years, have seen careers and reputations damaged or lost simply by being foolish or obnoxious in their words or gestures.

Ms. Skinner, who created “Alan” with Don Mackay, at least shows a sense of humor about excesses on the other end of the political spectrum. We learn that Roger’s current girlfriend, Courtney, a former art student, has signed up for “life drawing” classes and taken to wearing T-shirts bearing slogans like “Mind your own uterus” and, better still, “Carry yourself with the confidence of a mediocre white man.” She models the latter, Roger tells us, while drinking from a coffee mug that reads, “Be kind.”

Roger himself is presented as more of a patsy than a villain. Readily falling for Alan’s rants against mainstream media and “the ‘gynocracy’: a female dominated political regime which took over decades ago and has been spreading vicious misinformation about how all men are totally evil,” he lavishes more money than he can afford on a “gold donor” ticket to one of Alan’s conferences at a swank hotel. Mingling with other attendees, he hears jokes such as, “Drunk women are NOT asking to be raped. They are BEGGING for it.”

Back in his modest home, designed to cozy effect by the collective known as dots, Roger grows increasingly frustrated with what Alan has represented as the hypocrisy of a system that encourages female autonomy while insisting that men remain protectors and providers. Ms. Skinner’s sly, witty script conveys how easily grifters like Alan can manipulate information to make such arguments seem commonsensical. 

The playwright has an ideal messenger in Mr. Krasinski, who delivers a slow-building performance that’s ultimately as haunting as it is hilarious. Directed by Sam Gold — who wisely wields a lighter hand here than he has in various reinterpretations of Shakespeare and other classics — the actor finds humor in his character’s cluelessness and self-pity, sustaining a breezy, ironically cheerful vibe through much of the production.

When a late twist deflates what’s left of that mirth, Roger becomes at once more pathetic and more frightening, as underlined by a terse, chilling text message he receives from Courtney. He is the product of forces that have sent men and women alike scampering off to different silos, some admittedly scarier than others; in tracing his journey, “Angry Alan,” however funny, is likely to shake you to your core.