This study was conducted to identify the causes and specific mechanisms behind the asymmetric effects of brand activism on consumers. For this purpose, we examined consumer responses to brand activism, taking into account the relationship between brands, consumers, and the issue. Specifically, we conducted how the congruency (incongruence vs. congruence) between brand-consumer stances toward an issue affects moral trust, attitude toward the brand, and brand advocacy behavior. Furthermore, we verified the moderated mediation effect of brand identification. The results showed that the group with congruent stances toward the issue responded with higher levels of moral trust compared to the group with incongruent stances. This led to a more positive attitude toward the brand and higher levels of brand advocacy behavior. Furthermore, it was revealed that brand identification moderates the relationship between the congruency of brand-consumer stances toward the issue and moral trust. As brand identification increased, the impact of the congruency between brand-consumer stances toward an issue on moral trust became more significant, and this effect led to increased attitudes toward the brand and brand advocacy behavior. Our findings provide theoretical implications by verifying specific mechanisms through which consumers perceive brand activism. Additionally, there are practical implications for establishing strategies to minimize the negative effects and maximize positive outcomes of brand activism.