Transformative advertising research (TAR) suggests examining advertising’s transformational possibilities via the interactions between institutional actors at each marketing level to gauge its effect on society. We employ rhetorical institutionalism as a lens to examine the online speech acts of consumers as they respond to a brand activism campaign focusing on an environmental problem. Our data take the form of written comments by YouTube users and employ a research design using automated text analysis and qualitative thematic data analysis. Our contributions to TAR are threefold. First, we offer a preliminary conceptualization of the role of consumer language as rhetorical institutional work to advance TAR scholars and practitioners’ insight. Second, we highlight the role of linguistic tone and clout in giving speakers agency through which consumers as institutional actors create, maintain, and disrupt institutional logics and practices. Finally, we develop a tripartite classification of consumer speech acts used to support brand activism. We label these activist warriors, brand champions, and conscious consumers as typologies that deepen understanding of how consumers’ online speech may amplify brand activism, thereby contributing to advertising’s transformative outcomes. We conclude by outlining important managerial implications including how practitioners can adopt the tripartite classification to enhance brand activism campaigns.