“Welcome to being Black,” Little Marvin replied. It must get hard to believe your own eyes when your senses are being shocked over and over by cruelty, I said. “As the sinister elements outside the home ratchet up, that obviously allows for the cracks and fissures within each of them to be infiltrated by something malevolent,” the series’s creator, Little Marvin, said of the Black family at the center of “Them.” “But that malevolent thing, as sure as there is a supernatural component to our story, is deeply rooted in the emotional and psychological lives of these characters.” And yet, as the series, the first season of which drops on Friday, asks: Does that distinction matter when the danger is ever-present?