Because he wasn't a jew.
He was a Nazarite Israelite Judean.
Judah was invaded and occupied by the Edomites in 568 BC, their occupation of Judah/Jerusalem lasted until 70 AD.
They ruled Judah during the entire second temple period as the Rulers, pharisees and the law.
Both King Herrods during Jesus lifetime were Edomites.
After inhabiting Judah for hundreds of years, the Edomites became called Jews.
Biblical translations call all people in Judah by the mistranslation word Jew.
What Jesus actually said is, "those who say they are Judeans, but do lie".
In their correct translation, the words of Jesus make perfect sense.