SAN FRANCISCO – A studio that makes pornographic S&M-themed movies for the Internet recently took over a historic landmark that once housed the National Guard, unleashing a public debate about when — and where — propriety trumps tolerance.

Kink.com, which distributes its videos on X-rated Web sites with names such as “Hogtied” and “Men in Pain,” bought the old State Armory in the Mission District for $14.5 million, saying the vacant building’s dark Moorish architecture would make a perfect backdrop for fetish films.

“The basements in particular have a creepy, dungeony feel that is quite appropriate,” said Kink.com founder Peter Acworth. “We have spent a considerable amount of money on sets to get that dungeony feel.”

Acworth, 36, who planned Wednesday to oversee the first leather-clad shoot where guard troops trained for six decades, spent more than a year negotiating with the previous owner, keeping the deal private to avoid a backlash until the deal was done earlier this year.

Although city planners said the studio meets zoning requirements, residents and city leaders have reservations about allowing people to be tied up, spanked and poked with mechanical implements in a working-class neighborhood.

“While not wanting to be prudish, the fact that kink.com will be located in the proximity to a number of schools give us pause,” Mayor Gavin Newsom said in a statement this week.

He planned to organize a public hearing on Kink’s plans, even though city leaders acknowledge there’s little they can do to stop pornography production at the Armory.

Adding to the outrage is the fact that the building — erected in 1912, empty since 1970 and added to the National Register of Historic Places in 1978 — was sold after low-income housing advocates successfully killed proposals to develop the Armory into offices or apartments.

The Mission Merchants Association is in a bind over how vigorously to fight the porn studio, with some arguing it would provide an economic boost and others worried it would attract perverts, said Jean Feilmoser, president of the group.

“The Mayor’s Office is weighing in because they are perhaps buckling to pressure, but that place has stood empty for over 30 years and all the different entities in the Mission District tried to get something going there and ended up fighting each other,” Feilmoser said.

Acworth says he is a tad surprised by the squeamishness his vision for the Armory, which includes renting space to mainstream movie producers, has provoked.