NEW YORK >> Jenny Heinz, a longtime Metropolitan Opera and New York Philharmonic subscriber, calculates that over the past 60 years, she has been to hundreds of performances at Lincoln Center. But when she showed up this month at David Geffen Hall to see the Budapest Festival Orchestra, she was barred from attending when she refused to remove an 8-by-11-inch sign affixed to the back of her jacket.

It read: “NO! In the name of humanity we refuse to accept a fascist America.”

Heinz, 72, said she had been wearing the sign since she attended a protest outside Trump Tower in November. Though she had been looking forward to seeing the orchestra, partly because one of its cellists was almost stopped from entering the United States by President Donald Trump’s travel ban, she said that, given a choice between the performance and the sign, she chose the sign.

“At what point does one draw the line?” she said recently by phone. “We’re talking about freedom of expression.”

Officials at Lincoln Center refunded Heinz’s ticket, but this week they declined to discuss why she had been blocked from the performance. Heinz, though, said in an interview that during a later meeting she had with center officials — arranged by the civil rights lawyer Norman Siegel — the institution’s vice president for concert halls and operations, Peter Flamm, told her that signs were not allowed inside the performance halls or on the plaza outside.

The dispute seems to illustrate the conflict between those who view cultural institutions as bastions of free thought that should embrace activism and those who think that, to protect the primacy of the performance, political statements should be limited to those made by the artists and the art.

Timothy Biel, a fellow patron, who met Heinz outside the concert on the night she was turned away, later sent a letter of complaint to Lincoln Center. “The freedom of expression is the very foundation on which art is built,” he wrote. “Are you going to allow the dialogue between art and democracy to come to an end?”

In its only comment about the incident, the center issued a statement that said: “Lincoln Center’s founding mission is to bring the world’s greatest artists to the broadest possible audience. Every day we strive to provide an environment that cultivates the special and uninterrupted connection between a diverse array of performers and patrons, enabling a multitude of curated experiences for our 6.5 million annual visitors and artists.”

In his remarks about the sign issue, Flamm appeared to be relying on a 2002 federal court decision that said Lincoln Center could prevent leafleting and demonstrating on the plaza. Siegel said that a lawyer for Lincoln Center told him during a recent conversation that a message like the one conveyed by Heinz’s sign would have been allowed if it had been displayed instead on a T-shirt or on a button.

“From a policy point of view, what Lincoln Center is saying doesn’t make very much sense,” Siegel said. After all, he added, Heinz’s sign would not have been visible within Geffen Hall once she sat down, so it would not have disturbed the performance.

Policies at other institutions vary. Radio City Music Hall has a clear code, outlined on its website, that says signs and banners are not allowed “at any time.” Synneve Carlino, a spokeswoman for Carnegie Hall, said it had no specific policy on signs, but added, “However, if there is activity of any kind in the hall that disrupts the experience for artists or patrons, obstructs the view of concertgoers, or interferes with safety, etc., our policy is to address it immediately on a case-by-case basis.”

Heinz said that during her meeting with Flamm, she had urged the center to embrace debate, pointing to the Metropolitan Opera’s controversial 2014 production of “The Death of Klinghoffer,” about a Jewish American cruise ship passenger killed by hijackers from the Palestine Liberation Front, as an example of that sort of engagement. Those performances produced vocal protests by demonstrators who rallied inside barricades that lined Columbus Avenue outside Lincoln Center but did not reach into the plaza.

“The arts have always been political,” Heinz said. “Even if it’s disturbing to some people, it gets them to move for a moment into a place where they think about what is happening.”