The main issue this research paper aims to tackle is whether incitement to hatred, independently of direct incitement to violence should amount to the actus reus of persecution as a crime against humanity. Before determining whether hate speech can be treated as an international crime, this article assesses theories and current international legal standards in the field of freedom of expression in order to identify the space for such a drastic intrusion into this freedom. The most significant justification for an international criminalisation of hate speech in certain contexts is that it enables large-scale discrimination and threatens basic human rights, including the right to life, of the targeted out-group. Current international criminalisation, as interpreted by the jurisprudence of the Yugoslavia and Rwanda tribunals, still shows an overly narrow approach, excluding much of the hate propaganda that plays a vital role in the enabling of mass crimes. This article concludes that systematic incitement to hatred should be treated as a form of persecution, regardless of a call to violence, when the inciter has knowledge of the fact that his words might contribute to the commission of grave crimes or large-scale discrimination against the targeted out-group and the denial of human rights of its members.