The Treaty on the Prohibition of Nuclear Weapons (TPNW) is steadily attracting new adherents and is likely to enter into force in the next few years. Numerous states, NGOs, and scholars have praised the adoption of the treaty as a welcome addition to the nuclear non-proliferation and disarmament regime. But the treaty continues to face vocal resistance, including from a number of UN member states. Reviewing the main objections raised by sceptics, we suggest that the debate over the TPNW text and negotiating process in some ways constitutes a sideshow that masks the real source of opposition: profound differences over the acceptability of nuclear weapons. The most fundamental objection to the TPNW is that it delegitimizes the policy of nuclear deterrence.