A joke? And not even a particularly insulting one? He resisted the impulse to boggle visibly. Ha! That explains it. The bugger's trying to disconcert me with this unnatural display of politeness. Probably hoping I'll snap and hex him, that way he can play the Wounded Innocent and hex me back with impunity. Nice try, but two can play at that game! We'll just see who can be more unnervingly polite!
He deliberately forced back the usual logjam of sarky replies, in favour of a slight nod, and a casual, "Not to mention the effect on the decor. Blood would clash dreadfully, don't you think?"