If it was me, I would tell him that you are sorry, but you are recommending him to another trainer. I personally could not stand the thought of working that closely with a sicko like that. Sorry, but I just couldn't. If you can look beyond it, thats great....but not me. No way.
I would refer him to a male trainer....don't let some other female be his target, she might not be so observant or for lack of better words, strong enough to tell him to hit the road.