My wife was talking to a woman that was at a bar, dancing provocatively and sat at our table. We welcomed her and she started talking about her God. My wife said " I'm an atheist" and the woman got angry. Then I simply asked "what God are you talking about"? And we laughed when she stood up, pointed on the table and said the one true God, and she continued to banter but I think that is a very valid question if we talk about religion, haha!
In summary: If you want to get a God freak off your case, ask them which God they are talking about!