The quote is authentic, from Cassius Dio's Roman History 68.32 (Loeb edition, via Xiphilinus epitome): Jews in Cyrene under Andreas "would eat the flesh of their victims, make belts for themselves of their entrails, anoint themselves with their blood and wear their skins for clothing," with similar acts in Egypt and Cyprus under Artemion. Claims 220k dead in Cyrene, 240k in Cyprus.
This refers to the Diaspora Revolt (Kitos War, 115-117 CE) during Trajan's Parthian campaign. Jewish uprisings hit Cyrenaica, Egypt, and Cyprus amid ethnic tensions and messianic hopes post-70 CE Temple destruction. Archaeology confirms massive destruction in Cyrene. Casualty figures and atrocity details are typical ancient rhetorical exaggeration/propaganda, but the revolt was real, extremely violent on both sides, and crushed harshly by Roman forces under Lusius Quietus and others, nearly wiping out local Jewish communities.