Artist-provocateur Ai Weiwei became world famous mocking Chinese icons—dynastic artifacts, Tiananmen Square, Beijing’s Olympics—and has spent time in detention for his artistic expressions. One symbol of Chinese power he hasn’t pilloried is Xi Jinping, the country’s pre-eminent leader.

Mr. Ai, who is publishing a memoir on Nov. 2, says his mission is to call out governments and institutions when freedoms are threatened.