"There's not much excuse for performing "Little Sir Hugh" and none at all for presenting it as "entertainment" in its ancient form. (Even singing it as a "history lesson" seems perverse. As we know, its story is still believed plausible by millions.)"

Yes, the blood libel is still believed by millions, and that's precisely why the ballad can be used effectively (in the right hands) as a "history lesson."

"The past isn't dead, it isn't even past."

William Faulkner