SAN FRANCISCO, Oct. 24 — This Halloween, the Glindas, gladiators and harem boys of the Castro — along with untold numbers who plan to dress up as Senator Larry E. Craig, this year’s camp celebrity — will be celebrating behind closed doors. The city’s most popular Halloween party, in America’s largest gay neighborhood, is canceled. The once-exuberant street party, a symbol of sexual liberation since 1979 has in recent years become a Nightmare on Castro Street, drawing as many as 200,000 people, many of them costumeless outsiders, and there has been talk of moving it outside the district because of...