Does crossing a moral line justify collective means? Explaining how a perceived moral violation triggers normative and nonnormative forms of collective action

In three studies conducted in the United States, we examined whether a perceived moral violation motivates willingness to engage in normative and more radical collective action. Using value-protection and identity-formation models, we explored whether increased endorsement of moral convictions and relevant opinion-based group identification could explain such effects. Study 1, using the "travel ban" for Muslims as the focal issue, experimentally found that a strong violation, compared to a weak violation, increased normative and nonnormative collective action, moral convictions and opinion-based group identification. Study 2 replicated these results in a longitudinal design and supported a mediating effect of increased endorsement of moral convictions and opinion-based group identity. Study 3 used a real-world violation (the United States' withdrawal from the Paris climate agreements) to replicate the findings cross-sectionally. We conclude that a perceived moral violation motivates normative and nonnormative collective action because the violation makes one's moral conviction and opinion-based group identification more salient.