For years, advocates of the gay rights movement have said that their goal is to make the world a more tolerant place for homosexuals. They have just as adamantly claimed that they had no intention of educating young children in the complexities of human sexuality. Not so in Hollywood. Take, for example, the new animated film Boxtrolls, created by studio Laika. The film is a riff on the old Mrs. Doubtfire morality that suggests that all families are created equal, no matter what their composition. “Families come in all shapes and sizes,” the narrator of the preview says. “Even rectangles.”...