Feminist campaigns on social media platforms have recently targeted ‘manspreading’ – a portmanteau describing men who sit in a way which fills multiple seats on public transport. Feminists claim this form of everyday sexism exemplifies male entitlement and have responded by posting candid online photographs of men caught manspreading. These ‘naming and shaming’ digilante strategies have been met with vitriolic responses from men’s rights activists. This article uses debates around manspreading to explore and appraise some key features of contemporary feminist activism online. Given the heat, amplification, and seemingly intractable nature of the argument, it investigates the usefulness of Chantal Mouffe’s agonistic pluralism to unpack the conflict. Ultimately, however, agonistic theory is found to have limits – in terms of this case study as well as more broadly. Some final thoughts are offered on how feminists might best navigate the pitfalls of online activism – including the problem of ‘false balance’ – going forward.