Despite Rabbi Shmuley Boteach’s best efforts in “Kosher Jesus,” some Jewish teachers and their messages are not worth reclaiming. Whether because of their fanciful interpretations of the Bible or their odd religious agendas, they are best ignored. I have in mind not Jesus but Hyam Maccoby, the late, idiosyncratic religion scholar. Boteach says that his writings were, “more than any other works of scholarship,” his most trustworthy guide to early Christianity and essential to his efforts to construct a portrait of Jesus the Jew.

Maccoby, in works from the 1980s and ’90s, claimed that Paul — a conniving gentile pretending to be a Jew — distorted Jesus’ starkly political message. Boteach seems not to know that this strange, conspiratorial reading has been...