There's an almost imperceptible tic when Stryker mentions his students. No, not them. Xavier didn't mind if he was a prisoner but if he had harmed any of his students...on the outside he looks calm but there's a coldness that wasn't there before in his demeanor. He's also going to start working his wrists to try and get the ropes off very carefully so as not to be noticed. "Our school is no threat to you. Why are you doing this?" If he can talk him down first, he will.