Nebach. (On the other person, not you.) Have you thought that perhaps he does get it but simply has nowhere else to turn? Maybe be nice to him? You don’t give too many details. Maybe he’s desperate for a friend (or whatever it is that he wants from you) and he’ll back off a little if you’re nice instead of trying to push him away?
Make it your good deed for now. It may benefit you more than you expect.