There's a sneaky little pseudo-argument that's become all the rage in the age of combox and Facebook debates, though it's really quite old. It's called the genetic fallacy.
The genetic fallacy is the logically erroneous move of trying to dismiss your opponent's arguments by asserting that they are false not because of their own internal logic or because they're factually inaccurate but because their source is in some way untrustworthy, or because some outside force compels them to think in that way. There are plenty of examples we could give.
"Don't vote for that bill, it was written by the [insert opposing political party here]!"
The proposed legislation is being judged not on its own merits but its author. The bill might well cure cancer, make every citizen a billionaire, and ensure that the Yankees never make the playoffs again, but the speaker of this quotation won't consider it, because it's come from "the wrong people."
"Can anything good come from Nazareth?" (John 1:46)
Nathanael, soon to be an apostle of Christ, at first doubted even the possibility of Jesus being a prophet, not because of anything he had heard him say or do, but merely because of the town he came from. "He's from the sticks, what good could he be?" Nathanael was soon to find out how wrong he was.
"You only believe in God because you have daddy issues/you're genetically predisposed/you have a guilt complex. If you didn't have that, you would see God doesn't exist."
Here one individual's belief in God is denigrated by another and reduced to a product of biology or psychology. But notice the leap the speaker makes: because he deems the source of belief in God to be flawed or inadequate, he concludes that God's existence is likewise doubtful. But one does not logically follow from the other. Why one believes in God and whether God exists are two separate questions. I could present the completely nonsensical arguments for proving that Jerry Brown is indeed the governor of California ("Jerry Brown is governor of California because I had pizza for dinner last night"), but my non sequitur reasoning doesn't mean it is not the case that Jerry Brown is governor of California. Likewise, the reduction of religious faith to a neuron or a neurosis has no bearing on the existence of non-existence of God.
Keep an eye out for this faulty argument. It's all too common, and all too easy to fall for.