‘Militanz’ as moralised political violence has been applied by the radical Left since the 1960s, but has scarcely been defined in academic literature. In the particular West German context, ‘Militanz’ has been restricted to attacks against objects rather than persons, in contradistinction to the terrorist attacks of the 1970s. The Autonomist movement has further theorised this concept through the caveat of the ‘three Antis’ (racism, sexism, capitalism), against which they consider their violence to be morally justified. This article offers a genealogy and definition of this 1990s Autonomist ‘Militanz’ by relying on extensive archival research and oral histories collected within the Hamburg Rote Flora Autonomist milieu. It then interrogates both this concept and the group's claims to moral authority by working within the Autonomists’ own conceptual definition to apply ‘Militanz’ categorically to a riot during the 2017 G20 summit. The article disentangles the various ideological factions who took part in this riot, and challenges media discourses that the Rote Flora Autonomists were responsible. However, it also concludes that ‘Militanz’ as a purely ‘Anti’ stance cannot legitimate moralised violence without offering any affirmative definition of appropriate political action, lest all violence become acceptable ‘Militanz’.