Indeed - but what constitutes thinking? What constitutes existing? Descartes, you are assuming what you need to prove - next!
If I understand it correctly, the Christians were saying that proof of God's existence is evident by His creations, especially His special creation: us. To which the atheists' best response was, "Oh yeah. Well how do you even know we exist?" I mean, was that the best they had?
My son in law has a Bachelors degree in philosophy——HE’S AN IDIOT!