I think Xander knows that there really isn't a choice. When it comes right down to it, he does what he has to do. So I don't think he ever really meant the "no way in hell", but he wasn't going to make it easy on Spike either. And Spike is kind of showing a soft underbelly here too. Of course, right now Angel is the only one who's figured out exactly what that means. Well, Angel and us! We already know these two are in lurve!