Yes, this is a reasonable rationality quote. However, can we discuss the idea behind it because it's not entirely clear to me.

If the person maintains that there is any possibility -- as indicated by his "just in case", then is he not, necessarily an agnostic? What is so wrong about choosing the correct word? He doesn't believe in God but believes he could be wrong: he's an agnostic atheist.

Q: Am I being down-voted because I'm wrong? Am I beyond help??