Keegan is staging Guare’s “Six Degrees” … it’s a smart, topical choice. Guare’s plot still exerts an inexorable pull as a young black man named Paul — a movie star’s son, perhaps? — insinuates himself into several upper-crust Manhattan households. What Paul wants and why his “victims” allow themselves to be duped reveal a lot about Paul’s ambitions and limitations, while challenging how clearly white society can possibly see him. It’s is a fascinating script to revive in our era of celebrity culture and Black Lives Matter.