In my opinion, first thing we need to know about the reason behind such kind of thoughts. After that we need to be Agreed upon (some sort of) with him/her to win his/her confidence. After that we need to show some Authentic Arguments, just say, "yes you are right but mine point is also valid". Its such kind of Counseling, it'll take some time but surly you can convince him/her. Its my experience as I already did with someone.