What's the fallacy? With Russels teapot and that whole line of argument that atheists do as part of claiming non belief, I say I am happy to believe there is not a teapot orbiting in space. I believe it isn't true on the basis that the teapot wouldn't be a good explanation for anything, and it's entirely arbitrarily imagined. We can arbitrarily imagine an infinite number of things while reality is finite, and so such a teapot is unlikely. I ask this atheist if he is capable of believing that there are not sentient cucumbers on the planet Zog that worship his every move, or that he does not have an invisible pink dragon that sings him sweet lullabies each night. Because of how atheists try and justify their non belief, they must also have no belief about anything plainly ludicrous so long as there is no "evidence" (meaning, evidence they would accept, as in natural) against it, and so their position is irrational.
I don't know what you mean by G and ~G. God and about God? I've not been through formal philosophy education.