Why does Joe address Linden as the "skin of evil"?

Joe Coutts understands Linden Lark as an incurably evil person, someone with a fundamentally flawed nature. Joe holds Linden fully responsible for raping both his mother, Geraldine, and Linden’s ex-lover, Mayla; killing Mayla; and trying to kill Mayla’s baby. Joe hates him for these actions, yet to some extent he understands that such a person is infected driven by strong interior forces—in Chippewa myth, the Wiindigoo—even as he worries that acting to eradicate that evil would mean he was just as bad himself.
Joe is portrayed as being a fan of Star Trek – The Next Generation. He processes much of the information that comes to him in real life through analogies to the television show. Joe associates Linden with an evil humanoid on the show, featured in a specific episode, “The Skin of Evil.” He and his friend Cappy both refer to Linden with that episode’s title.