I've found the best way to deal with people like that is to gently mock them. When he says no atrocities were committed by Christians, you can reply, "Yah, that whole Dark Ages thing was just a Liberal Coverup." When and if he gets belligerent, you could ask him, "You pray to Jesus with that mouth?" You could make jokes, "If Jesus were alive today he'd tell you to knock it off." Or, "Oh, Mike Huckabee, yah, he's the guy who defends incest and child molestation."

Reason and logic doesn't work with these people. If it did, we'd be in a different place. So the best thing to do is turn their statements against them, gently, and humorously.

Live and let live, probably a good idea to set a some boundaries and not discuss religion or spirituality with him. Your co-workers or team mates and not friends... keep it simple!
I’d rather have a mind open by wonder then one closed by belief!
What do we all know really? People just walk around dead convinced of their truth, actually it’s more like we are all pretending. Religion is one of the biggest human dividers, next to politics and governments.

1. You've made it clear to him that you are not into religion and you say that you are tired of being nice. 2. And, you say you'll respect his right to believe what he wants if he respects your right not to. 3. You are concerned about the reaction of your corporate overloards.

Is it possible in your corporation for you to talk over this situation with one or more of the corporate people? It would be good to know how they feel about what's happening to you. Some may see the guy's behavior as inconsistent with their purposes and goals for the corporation and disruptive to the achievement of their goals.

Regarding points 1 and 2 above, simply repeatedly tell him that you are not interested in religion. Do so in a simple manner, and repeat it like a broken record. Avoid discussing the issues with him. Avoid elaborating. Look him straight in the eye and stay completely calm and firm. Most likely he will recognize that he is getting nowhere with you and he will give up. But you need to be simple and persistent.

Consider the book titled, "When I Say No I Feel Guilty" at Amazon. It's excellent.

Good luck with this.