The T-850 had killed whatever snakes he'd come across. Granted, that wasn't all of them.. but he did what he could. As best as a near-indestructible cyborg assassin from the future could do, anyway.
He heard the words and watched as the witch turned evil. His scan indicated that she was human, and yet.. she somehow affected her environment, even though there was no rational reason why. He filed that information under his Magic category files.
He just stared at her, holding his shotgun. Looking at her, though it seemed as he was a statue. Then he spoke. "Negative. Human survival is priority." The concept of playing, as Willow had said, was foreign to him. Perhaps it was another human expression or something. But he would do what was necessary to protect the residents.. to protect John.