Prov 18:19 "A brother offended is harder to be won than a strong city: and their contentions are like the bars of a castle"
Your positive support will help more than anything. And what I mean by that is, support him, uplift him, and love him. In these relationship type situations, its difficult because you are trying to battle a belief. Imagine how upset you get when someone says God isnt real. Its because you believe deeply that He is (well....He is lol) and they have just dissrespected that belief. On a different scale, this is whats happening everytime you say something.