The past several years have seen rising hate crimes, terrorist attacks, and broader extremist movements, with news reports often noting that these movements can be traced back to fringe online communities. Yet the question remains why such online groups appear more likely to foster radicalization than those in other contexts. This netnographic case study demonstrates how sexual appeals in fringe online communities facilitate the development of extremist ideologies. Specifically, the cognitive effects of sexual arousal combined with the social norms of such communities contribute to the acceptance of hate speech and fringe ideologies while reducing the extent to which audiences evaluate rational arguments and competing points of view. Thus, sexual appeals paired with messaging or imagery that promotes fringe points of view, which can be more freely expressed in small online groups than in other contexts, are more likely to result in intended attitudinal and behavioral changes—in other words, extremism.