When moderates endorse extreme means: moral foundations, powerlessness and support for illegal climate action

Political extremity is commonly attributed to the strength of moral conviction, yet moral conviction also sustains lawful participation. This study asks when moralisation channels citizens towards lawful engagement and when it becomes associated with support for illegal means, taking climate change as a case in which both repertoires are active. Drawing on Moral Foundations Theory and the literature on normative and non-normative collective action, a nationally representative online survey of South Korean residents aged 19 and over (June–July 2025; N = 1,970; regression N = 1,895) was analysed using hierarchical regression, modelling support for lawful and for illegal environmental action as distinct outcomes predicted by social solidarity, ideological radicalism and perceived climate injustice, with three binding moral foundations—Purity/Sanctity, Authority and Ingroup loyalty—entered as moderators. The outcomes had different antecedent structures: support for lawful action was associated with collective efficacy, perceived inequality, social trust and intergenerational justice, support for illegal action primarily with powerlessness and anarchism. Of 54 interaction terms, 25 reached p < .05, with small coefficients. Purity/Sanctity and Authority generally attenuated, and in one case reversed, the associations between grievance, ideology and support for illegal action, contradicting the expectation that sacralisation lowers the threshold for extreme means. The single systematic exception was powerlessness, whose association with support for illegal action strengthened as either foundation increased. Extremity therefore arises not from a level of moral conviction but from its conjunction with perceived inefficacy: the boundary between moderate and radical engagement is conditional rather than dispositional, and keeping lawful channels credibly effective is central to governing it.