Seriously? Bullshit.
It's true. That's not to say that there aren't any reasonable or decent people (by human standards) who don't believe in God, but one can trot out all sorts of statistics that would support that believers do behave better in society in general.
Yes, Shadowdancer.
If you believe that there are absolute moral standards; that there is absolute truth; that Someone is watching you; that there is ultimately perfect justice; that there is a penalty to pay for disobeying God's law -
yes, it affects your behavior. For instance, some day you'll answer for your use of profanity. Mock if you will. You will answer for it.
Myself, I don't use profanity. Because God says not to, and I know He hears what I say. See? My belief system just affected my behavior.