I wonder if the student was actually challenging you (and every other male in the room) for the alpha male role? When considering behaviour management, it's useful to determine the perpetrator's hidden agenda. If I wasn't being observed, my response would be a comment to make everyone laugh at his lack of sexual experience (e.g. "Just make sure I can see your right hand"). Risky strategy of course. As an observation was in progress, a politically correct response was appropriate. Just go along with the nonsense until you qualify, then find your own strategies afterwards. On another note (English), in this case it's "curb", not "kerb". And I'd probably say "defuse" rather than "diffuse".