When I say you, I don't mean you:
Most don't, it's when people say they don't believe, and then characterize who God is based on what they believe. For example:
Person A: God is evil!
Person B: no he's not, have you heard about Jesus...
Person A: God's not real.
Person B: okay, but you just said he's evil as though he's real.
If you believe God to be a fictional character, treat him as such, with the consensus of what believers say about him. Otherwise you make it sound as though you believe but don't want to accept it.