First used in the atheist forums in Yahoo! Message Boards - where investigation into the stories in the Christian Bible, shows that (mere) humans are capable of better moral conduct than the biblical literal God.
For example: Instead of smiting the men, women and children of Sodoma and Gomorrah, God could have intervened into their lifestyle and taught them better ethics and responsibility, rather than the wrathful smiting of them. This example of moral decision shows that one is better at imagining moral conduct, better than God.
My god is BT your G.