BEIJING - Sixteen years after the bloody crackdown at Tiananmen Square, China's grip on dissent has tightened. From religion to the media, political activism to the Internet, Hu Jintao's regime watches all - and silences any challenge to the Communist Party. Members of non-sanctioned churches risk detention, potentially incendiary chat rooms are shut down, newspapers are kept on a short rein and employees of foreign news organizations have been arrested and accused of spying. Last month, an international conference on democracy planned for Beijing was canceled. When Hu came to power in 2002, many had hoped that the new president...