My understanding is that the term "blood libel" refers to bogus charges starting around the 12th century that Jews drank the blood of children in secret rituals. "Blood libels" against the Jews, thoroughly reprehensible in their own right, are not about the cruxifiction of Jesus.
That's always been my understanding as well. There was a discussion of this in the media about six or eight months ago when Egyptian papers started talking about Jews supposedly killing children to use their blood in making matzo dough. That's one reason I was surprised to see some critics of Gibson's film use the term blood libel to refer to the "may his blood be upon us" line from the Gospels.