Ten weeks of protests, some huge, a few violent, culminated Monday with a shutdown of the Hong Kong airport. Ominously, Beijing described the violent weekend demonstrations as "deranged" acts that are "the first signs of terrorism," and vowed a merciless crackdown on the perpetrators. China is being pushed toward a decision it does not want to make: to use military force, as in Tiananmen Square 30 years ago, to crush the uprising. For that would reveal the character of President Xi Jinping's Communist dictatorship, as well as Beijing's long-term plans for this semi-autonomous city of almost 7.5 million. Yet this...