The tension in Hollywood over declining box-office receipts heated up on Thursday as the head of the trade organization for movie theaters accused the chairman of the Walt Disney Company, Robert A. Iger, of leveling a "death threat" against his industry. The trade official, John Fithian, president of the National Association of Theater Owners, was responding to a statement by Mr. Iger to Wall Street analysts this month that movie studios need to accommodate changing consumer demand by releasing films simultaneously in theaters and on DVD.