This explores how message framing influences consumer reactions in brand activism. Based on data from 304 participants, it analyzes the relationships among gain–loss framing, inference of manipulative intent, psychological reactance, consumer responses (such as brand attitude, purchase intention, and negative word-of-mouth), and perceived value alignment between the consumer and the brand. The findings indicate that loss-framed messages induce a higher inference of manipulative intent compared to gain-framed messages. Moreover, the inference of manipulative intent has a positive impact on psychological reactance. Consequently, psychological reactance negatively impacts brand attitude, whereas it positively influences negative word-of-mouth intentions. Moreover, increased congruence in values between the brand and the consumer regarding the social issue alleviates the detrimental effects of psychological reactance on both brand attitude and purchase intention. Conversely, it enhances the influence on negative word-of-mouth intentions. The mediation and moderated mediation effects varied across consumer response types. Specifically, the indirect effect through inference of manipulative intent and psychological reactance was significant only for negative word-of-mouth intention. This study offers practical implications for developing effective communication strategies through the investigation of message framing within the relatively underexplored field of brand activism.