RUTHFULLY YOURS

She was quoted as describing a double standard whereby officials and media figures assert that the perpetrators of Islamist terrorism “do not represent Islam, that Islam is a religion of peace, etc.,” and look for explanations of how they went astray. When the terrorists are white supremacists, on the other hand, “attempts to understand the sources of their radicalization or their perverse moral reasoning is beyond the pale,” and anyone who wants “strong borders and immigration control” is “painted with the same brush” as the racists. Although she called white supremacy “odious” as well as perverse, a headline on the public broadcaster CBC’s website matter-of-factly described these as “white supremacist comments.”

Such campaigns have become common. The emerging call-out culture in the U.S., Canada and elsewhere in the West bears more than a few similarities to China’s Cultural Revolution, in which writers, artists, doctors, scholars and other professionals were publicly denounced and forced by mobs to engage in ritual self-criticism. The goal is not to persuade or debate; it is to humiliate the target and intimidate everyone else. The ultimate objective is to destroy independent thought.

In China, people in my father’s generation—he was born in 1957—learned to keep their heads down and to watch what they said, even to their closest friends, for fear of being accused of thought crimes. Privacy and trust were dissolved, and informants were everywhere. Similarly, one of the most chilling aspects of Ms. Ford’s case is that the media didn’t hesitate to use private conversations to condemn her. Even if such methods can expose some genuinely bad people, is it worth living in a world where we are afraid to say what we think, even to our friends?

The presumption of innocence is a fundamental tenet of Western law. Yet it is increasingly abandoned in the rush to enforce orthodoxy and destroy political enemies. The mobs pile on, destroying lives, careers and reputations with gleeful abandon. They claim to act in the name of tolerance, compassion and diversity, but their commitment to these principles is purely abstract. In practice they are intolerant and cruel, and they demand total conformity.

Today’s China shows where this all leads. My mother and I emigrated to Canada when I was 13, and I eventually began speaking publicly against human-rights abuses. My father back in China, threatened by security agents, broke off contact with me. Beijing engages in massive, brutal repression of religious minorities, including Tibetan Buddhists, Uighur Muslims and practitioners of the Falun Gong spiritual discipline—even extending to the harvesting of human organs. That’s what happens when one party achieves a total monopoly of ideas by acting on the belief that any means are justified to destroy their opponents.

China did not become a tyranny overnight. Too many people in my father’s generation chose not to stand up for their neighbors, friends and even family members when they were under attack. They learned to obey instead of challenge, to pick sides rather than think for themselves. They assented to obvious lies because they didn’t want the mob to turn on them next.

Such practical-minded decisions to place reputation and safety above truth allowed evil to accumulate. Personal compliance became collective complicity, and China was lost to totalitarianism. Don’t let it happen here.

Ms. Lin is an actress and human-rights advocate.