Filmmaker John Waters achieved what he calls a “sort-of fame” based on his bad taste and others’ bad reviews. “If someone vomits watching one of my films, it’s like getting a standing ovation,” he once wrote. Sincerely shameless during the 1970s, when the obscenity of movies such as Pink Flamingos shocked audiences, Waters seems to have softened into his 70s; the latest role in his filmography was a part in Alvin and the Chipmunks. His darkly subversive humor—a lifelong motif—may have long since migrated from the fringes of counterculture into the mainstream, but he, his legacy and his trademark pencil moustache retain cult status. With a retrospective of his visual art opening at the Baltimore Museum of Art, Waters—whose genteel manner belies his proclivity for shocki...