I think it's you who clearly doesn't understand. Jewish people can be identified by their DNA. There's no such thing as 'Christian DNA'. You cannot identify a coin collector, a train spotter or a car enthusiast by their DNA! If Jewishness wasn't at all linked to ethnicity, then similarly there would be no point in testing for Jewish DNA. They're a Semitic people who have for two thousand years mixed with Europeans and that has resulted in Jewish ethnic groups.
The fact that you maintain there is no such thing as Jewish ethnicity, despite the law stating otherwise, as well as Wikipedia, illustrates you simply won't admit you're wrong. I have nothing more to add on this matter, as I don't see there's any point debating with you. Enjoy the game tomorrow, if you're there!