The growth of corporate activism on contentious social issues creates a puzzle as to why companies would risk engaging on divisive topics. Indeed, a mixed body of evidence identifies that such activism often reduces stakeholder support. We shed light on this puzzle by reversing attention to the costs of not engaging in corporate activism. Grounded in the cognitive model of stakeholder behavior, we theorize whether and when consumers will negatively respond to corporate silence on a social issue based on the visibility of silence. Our theory also suggests that peer activism and market niche are pivotal contingencies that exacerbate or mitigate such negative responses. Using a rigorous within-company cross-platform difference-in-difference econometric model, we find support for our theory and uncover substantial costs of corporate inaction.