[ If Spike knew that the other wasn't so sure about his actual existence, there would be a whole lot more laughter in his face in place of fangs. The fangs would surely come later, but with how open the vampires of this place are and the Blood Shack being right there, non-believers always come across as a bit daft to him.
The punches hit, but doesn't do too much. He's used to getting punched in the face and although the way they make his head jerk to the side keeps him from actually biting, it doesn't really deter him from his goal of nom. ]