Not sure what you mean by "faith healer," but outside of that, the situation of doubters always doubting cannot be solved by intellectual argument. It simply perpetuates it. Even personal testimony of how Jesus changes our lives today will not compel the doubters. They have to take an honest look - which it seems they cannot do. That doesn't mean that you or I should stop trying. Jesus affected my life dramatically when I turned to Him, but no matter how hard I try, even friends look at me cross-eyed..."Happy for you, dude," is where it ends. Yet, they will know we are Christians by our love when we assemble together, maybe?