It was not your typical Broadway or West End crowd.

On Thursday night, audience members passed through airport-style metal detectors into the cavernous and maze-like Ronald Reagan Building and International Trade Center. At least two wore red “Make America Great Again” hats; one sported a blue “pro-life” sweater.

Outside the amphitheater was a placard for the one-night only show FBI Lovebirds: Undercovers, accompanied by a quotation from the Politico website, “Hamilton for the MAGA crowd”, a reference to Lin-Manuel Miranda’s hit musical, a distinctly un-Trumpian celebration of immigration and racial diversity.

What followed inside, over nearly two hours, was a staged reading of text messages between FBI agents Peter Strzok and Lisa Page, interspersed with chunks of their congressional testimony.

Strzok, “regarded as the No 1 counter-intelligence agent in the world”, was among the leaders of the special counsel investigation into Russian interference in the 2016 presidential election. But he was axed when it emerged he had been trading indiscreet, Donald Trump-bashing tests with Page, with whom he was having an extramarital affair. Page has also left the FBI.

The inspector general’s office found no evidence the attitudes they expressed affected their investigatory work. Even so, they provided fodder for Trump and his constellation of media allies to claim the president was the victim of a “witch-hunt” and say it was high time to investigate the investigators.

FBI Lovebirds: Undercovers had been slated for Washington’s Studio Theatre, which typically has a rather different political sensibility, but the performance was cancelled for security reasons. In a statement, aside from mentioning “open and violent threats made against the theater” they also added: “Media reports have made us aware of undisclosed details about the event.”

As a result, it was shifted to the Reagan building on Pennsylvania Avenue, close to the White House, the Trump Hotel and the US Capitol.

Strzok was played by Dean Cain, who has declared himself a “Trump guy” and sometimes turns up as a talking head on conservative Fox News; his Twitter feed is littered with retweets of rightwing conspiracy theorists and the National Rifle Association. In the four-page programme, Cain, who starred as Clark Kent in Lois and Clark: The New Adventures of Superman, was described as “athletic and intelligent”.

Strzok was potrayed here as preening, self-satisfied and smug. Cain was perfectly cast.

Page, who has brown hair, was played by Kristy Swanson with blonde hair and a knee-length skirt. Swanson played the original Buffy Summers in the 1992 film Buffy the Vampire Slayer, and also had a role in Ferris Bueller’s Day Off. This week she retweeted a post by Mike Cernovich, who has promoted baseless claims that Hillary Clinton was part of a child sexual abuse ring in the basement of a pizzeria.

Directed by Richard Kuhlman, both actors delivered perfectly respectable performances despite a lack of stage experience. Indeed, despite everything, the night was not devoid of artistic merit.

The text messages made for compelling, excruciating and, on occasion, amusing verbatim theatre. Page sighs at one point: “Oh, this is painful. Annual ethics training.” She describes Trump as an “enormous douche” and declares: “The man has no dignity or class. He simply cannot be president.”

Most infamously, Page asks Strzok for reassurance that Trump is “not ever going to become president, right? Right?!” Strzok replies: “No. No, he won’t. We’ll stop it.” He squirms in his chair as he tries to explain that to Congress.

The play shifts back and forth in time to include scenes where the pair are cross-examined by two congressman, composite characters drawn from real hearings on Capitol Hill. Page is reminded that she wrote: “God, Trump is a loathsome human.” A Congressman asks: “What did you mean by that?” Page replies: “I don’t recall.”

Playwright Phelim McAleer rightly highlights an offhand comment by Strzok: “Just went to a southern Virginia Walmart. I could smell the Trump support.” A congressman presses, “What did it smell like?” and demands, “Could you also smell the Clinton support?” Strzok admits: “I have never tried.”

The exchange was likely to confirm many in this audience’s suspicions of how liberal America views them (“deplorables”). There was a standing ovation and shouts of “Bravo!” at the end. The mainly white gathering of nearly 500 will have gone home with their prejudices unchallenged, their faith in Trump strengthened.

Audience member Brian Green, 66, an aerospace consultant from the Shenandoah Valley, said: “A large part of the media have ignored this side of the investigation, who took part, what were their biases. It seems pretty clear there’s a story to be found there.”

But as a piece of drama, the problem with FBI Lovebirds: Undercovers is a lack of moral heart or sympathetic character. No one comes out of it well. The implied “hero” of the piece is off stage and named Donald Trump.

McAleer, 52, wearing a white flannel suit and pink shirt, told the Guardian he finds Trump’s presidency “very interesting and invigorating” and that working on the play made him question the FBI’s conduct. “I think it led me to definitely believe that there to be more investigation of the malfeasance of FBI officers who have politicised the FBI,” he said. “If if we had J Edgar Hoover’s texts, they might read like that.”

McAleer, who is from Omagh in Northern Ireland and has lived in the US for 10 years, acknowledged he has met resistance to his work. “The arts tend to be liberal and Democratic, but I think the theatre community is like a Maoist wing of that. There’s nobody more left than the theatre community.”

Two and a half years into the Trump administration, theatre has offered some pointed productions of Shakespeare’s Julius Caesar and Richard III, as well as bracing new plays such as Shipwreck by Anne Washburn and Building the Wall by Robert Schenkkan. The theatre is usually a space for progressive values. But the enthusiasm roused on Thursday night suggests an appetite to contest it.