My favorite scene in the recent documentary “Maria by Callas” is when, after a seven-year absence, the world’s most famous diva returns to the Metropolitan Opera in 1965. A TV journalist visits the theater to interview young men who have been waiting hours — overnight, even — for tickets. And while none of them are explicitly gay, it’s no secret that they are.

There’s Dennis, with beaming eyes and extravagant phrasing, crowning Callas as “the greatest”; and Lex, dead serious in claiming that to miss her performance would be “a crime.” A third guy can’t stop smiling as he says she’ll receive a 30-minute standing ovation, even if he has to be the only one standing (though he’s sure he’ll have company).

Company, indeed. This heartwarming moment is a postcard from the past, preliberation gay men unintentionally announcing to the present: We have always been here. If you don’t think so, just read the hyperbolic diva worship in Walt Whitman’s poetry from the 19th century.

But opera, an art form that has existed for several hundred years, has only recently begun to reflect the lives of some of its most ardent fans with contemporary works that tell the stories of gay men, as well as the rest of the lesbian, bisexual and transgender community. The latest example is Iain Bell and Mark Campbell’s thin but often charming “Stonewall,” which premiered on Friday at the Rose Theater in a production by New York City Opera.