[That people would like to believe they are vampires isn't so hard to swallow; he's at least considering the possibility that this is legitimate. On the other hand, the likeliest possibility is that none of this is real, and rather than subscribing to a slightly alternate sort of sanity he's gone off the proverbial deep end.
Either way, he doesn't want to find out like this. He twists and pulls, trying to loosen that grasp-- he'd wriggle out of his shirt if he had more space to do it in-- stabbing blindly at Spike's side as he does. For good measure he manages to stomp his heel soundly on the vampire's foot. Breaking a couple of toes would please him inordinately.]