In this article, we introduce the concept of “anti-activism” and explore the possible impact of anti-activist action in Hong Kong. We define anti-activism as a form of countermovement intended to discredit, distract, and even harass activists in voluntary social movements. Our data and analyses are based on field observations, interviews, and primary documents collected in Hong Kong during 2012–2018. We focus on the case of the protest campaign against the quasi-religious group Falun Gong 法輪功 to develop our argument. We find that anti-activists do not try to win public support for their cause. Instead, they succeed most effectively through the process of disrupting and discrediting voluntary activists to arouse tension, conflict, suspicion, and annoyance in the public. They discredit not just their opponents but even themselves, and, thus by extension, they discredit social movement activism per se, polarize public debate, and in a way undermine the integrity of civil society in Hong Kong.