A pet shop owner in Yongin, Korea, about 25 miles south of Seoul, set off an international incident recently with an advertising sign featuring . . . a puppy. In the sign, a dog’s head replaces that of Mao Zedong in the portrait hanging at the northern end of Tiananmen Square. Last Tuesday, China’s Foreign Ministry summoned a South Korean diplomat to protest, and the shop’s owner immediately pulled down the sign and apologized to Beijing. What’s wrong with this picture? First, China’s authoritarian state tried to censor an image appearing in a democracy—and the democracy bowed. Yet there is...