TOKYO - Controversy over "The Cove," an Oscar-winning documentary about the annual dolphin hunt in a Japanese village, has widened into a debate over free speech in the country. Three theaters last week canceled showings of the movie after they were swamped with angry phone calls and threatened with noisy protests by nationalist groups. It was banned on a US military base in Japan as too controversial, and 23 other theaters are still deciding whether to show the film, according to Japanese distributor Unplugged. After the cancellations, a group of Japanese journalists, academics and film directors signed a letter urging the theaters not to back down and saying the issue "underlines the weakness of freedom of speech in Japan." Freedom of speech is guaranteed in Japan's constitution, but many Japanese are wary of unruly demonstrations. Nationalist groups, known for blasting slogans from truck convoys and handheld loudspeakers, often use the threat of protests as leverage. Two years ago, angry phone calls led several theaters to cancel showings of "Yasukuni," a movie about a Japanese war shrine that honors fallen soldiers, including executed military leaders convicted as war criminals. On Wednesday, over 600 people crammed into a civic hall in Tokyo for a rare chance to see "The Cove," with lines forming hours before the doors opened and viewers spilling out into the lobby to watch via a video feed. Outside of small private showings, it was the first time the movie has been screened in Japan since October, when it was shown at the Tokyo International Film Festival. The event had originally been planned to discuss the movie, which shows bloody scenes of a dolphin slaughter filmed by hidden cameras and portrays local fishermen as rough goons. But instead the event focused on the theater cancellations, reflecting the changing debate around the film. "Protesters only threatened to do bad things, and then theaters got scared and pulled out," said Hiroyuki Shinoda, chief editor of "Tsukuru" magazine, which organized the showing. Shinoda, who signed the protest letter last week, urged those present to contact theaters and ask that the movie be shown.