I absolutely love religious debates...
I know this one's focus isn't really God vs. no God, but when the debate turns into that it's essentially this:
Believer: "I beleive God is real. I don't need physical proof. I have faith."
Non-believer: "You're irrational for believing in something without proof."
Both sides have given very good points in this debate (IMO), and obviously the demonstrative conversation was a general one, but a lot of times that's basically what the debate boils down to.
Sometimes it's the opposite way around with the believers calling the non-beleivers irrational. Other times it's both.
Either way it's amusing to watch...
Edit: I'm not referring to anyone in particular with this post. (Read: [insert statement to cover my ass.])