blood libel is supposed to mean accusations that jewish people eat/drink blood (e.g. Protocols of the Elders of Zion, and one of the many factors that led to the current cultural idea of vampires). it's often mistakenly applied to people describing Israel as "bloodthirsty", but like, that term is universally used for evil of all different ethnicities and religions. that mistake then gets further abstracted into "being against genocide is blood libel".