We cannot overstate the importance of understanding that Christianity began with Genesis; with Moses, with Abraham, and all the Prophets; and Christ—His Birth, His Life, His Death, His Resurrection—being the confirmation of their prophecies and fulfillment of the law. Judaism must be seen as a deviation, a heresy that rejects and defames the Messiah.
Thus, to claim that "Jesus was a Jew" is to assign to the Messiah the identity of those who reject the Messiah. It is contradicting, misleading, and blasphemous.