Here's something to throw back in the face of the next Christian who asks you how you can be a moral person without belief in God, or without following the teachings of the Bible. Your reply should go something like this:

Your religion teaches that Adam and Eve ate the fruit from the tree of knowledge of good and evil, right? This gave the knowledge of good and evil to them, and to all humans, right? Therefore everyone knows the difference between good and evil. Even atheists.

You can never lose when you use this argument, because if God does not exist (and the fruit/tree story is false) then how come Christians know good from bad? And if it is true, there are no conditions attached to the knowledge of good and evil. Everyone has that knowledge, whether or not they believe in God, and whether or not they have a personal relationship with Jesus, follow the Bible, etc.

Whichever is the case, by their own Bible teachings, Christians prove that the Bible is not the source of morality.

Checkmate.