Stallworth makes contact with the KKK by chatting them up over the phone, but when the time comes to meet IRL, he enlists Flip to be his "face." Flip, we discover, is Jewish. Adam Driver, the actor, is not, which I think is important, because Stallworth observes that he's "passing" -- Flip denies the categorization, but once he realizes just how much antisemitism lurks in his own city, it gives him pause.
Stallworth and Flip soon form a dynamic duo of anti-racist cops, which in 2018 is enough of a paradox to add to the headspinning title, and their scenes together are extraordinary. When the most loathsome, violent of the KKK goons has Flip in his sights and accuses him of being secretly Jewish, Stallworth swoops in and saves the day, and does it in a way that doesn't blow the investigation.