In the Old Town historic district here, tourists and shoppers stroll brick sidewalks along King Street and peer into a wide range of boutiques — rug shops, antiques dealers, a cheese shop, even a comic book store. Old Town’s latest offering, though, has been stopping visitors in their tracks since it opened in January. It is called Le Tache, a “couples boutique,” more commonly known as a sex shop, which is sandwiched between art galleries whose offerings are more common in Old Town than colorful vibrators and steamy DVDs. The boutique’s owner leased the building after a dispute between the...