Well, I'm not sure. I don't really go in for evangelism, in the normal sense of the word. That's because I think we all (Jew and gentile, Christian and Muslim, pagan and atheist) end up in the presence of God, anyway. So I feel no pressure over other people's faith - that's their business, and they can have the relevant conversation with God when it is time for them to do so.
I would feel sad that someone who thinks themselves a Christian has missed the crucial point of the crucifixion, which was nothing if not a demonstration of love. And a love so intense that not even life itself was too great or dear a possession to lose for it's sake. So, I guess I wouldn't say much, and just get on with the business of working on my own belief system. And when I've done that, maybe I'll have a better answer for you.
Best wishes, 2RM.