Christianity explains rationality and reason, because it follows that there is a consistent God who created everything that is, and that the creation is a reflection of God.

Atheism, to account for the universe, must surmise that anything is possible. And in the process, undermine the very basis of rationality and reasoning. Atheism is, at its core, an irrational and unreasonable faith, which isn't even based on evidence. Ironic that it turns out to be the exact opposite of everything so-called "free thinkers" hold dear.