One dilemma faced by policy makers is the choice between banning a harmful behavior and allowing the behavior to continue but with mitigated harm. This latter approach––a harm reduction strategy––is often efficacious, yet policies of this sort can be unpopular if people morally oppose the target behavior (MacCoun, 2013). This raises interesting questions for understanding how judgments of harmfulness relate to moral opposition. In four studies (N = 1,088), including one U.S. representative sample, we found that increased moral opposition to cigarette smoking, risky sex, and gun ownership, was associated with less support for e-cigarette use, pre-exposure prophylaxis, and gun safety training, respectively—with one critical exception. When news broke of “vaping sickness” in 2019, we no longer observed this relationship. Interestingly, judgments of harmfulness of both gun ownership and risky sexual behavior, though correlated with moral opposition, positively predict policy support, suggesting that it is possible to judge a behavior as harmful but otherwise acceptable, and in that case harm-reduction policy is also acceptable. Together, these results highlight the multi-faceted nature of moral opposition and its implications for real-world policy.