  Social media platforms like Facebook and Reddit host thousands of
user-governed online communities. These platforms sanction communities that
frequently violate platform policies; however, public perceptions of such
sanctions remain unclear. In a pre-registered survey conducted in the US, I
explore user perceptions of content moderation for communities that frequently
feature hate speech, violent content, and sexually explicit content. Two
community-wide moderation interventions are tested: (1) community bans, where
all community posts are removed, and (2) community warning labels, where an
interstitial warning label precedes access. I examine how third-person effects
and support for free speech influence user approval of these interventions. My
regression analyses show that presumed effects on others is a significant
predictor of backing for both interventions, while free speech beliefs
significantly influence participants' inclination for using warning labels.
Analyzing the open-ended responses, I find that community-wide bans are often
perceived as too coarse and users instead value sanctions in proportion to the
severity and type of infractions. I report on concerns that norm-violating
communities could reinforce inappropriate behaviors and show how users' choice
of sanctions is influenced by their perceived effectiveness. I discuss the
implications of these results for HCI research on online harms and content
moderation.
