BEIJING At 5 p.m. on Jan. 24, Li Datong's status went into a deep chill. Mr. Li, a Tiananmen protest veteran and a rare crusading editor still allowed to work, learned that "Freezing Point," his weekly magazine, had been closed. The proximate reason: a lengthy article smashing official history of the 1900 Boxer Rebellion, when a peasant cult killed more than 230 foreigners in a spasm of...