From Amazon.com’s description of Vitz’ book:
Disappointment in one’s earthly father, whether through death, absence, or mistreatment, frequently leads to a rejection of God.
Professor Vitz does not argue that atheism is psychologically determined. Each man, whatever his experiences, ultimately chooses to accept God or reject him.
And again, quoting you paraphrasing Vitz:
[I]f belief in God is nothing more than a desire for a father figure, then atheism is nothing more than a desire to kill that father figure.
The default position implied in these claims is undoubtedly the belief in a god. Either you accept that this god does exist, or you reject this god. Vitz doesn’t allow for any other alternative. That’s a straw man argument, because the most reasonable stance would be to reject any hypotheses that lack evidence — like the hypothesis for the existence of gods. The difference is that most atheists don’t reject the possibility of gods, just the claim for their existence.
Vitz mentions a couple of famous atheists with father issues, but fails to prove any causality. Could just as well be that the intensity of their atheism was a result of their interactions with Christians.
So, I have to correct my comment thusly: either Vitz’ line of reasoning presupposes the existence of gods, or it’s based on a Christian worldview that sees itself as the default position. Either way it’s a flawed argument. Granted, it’s just as flawed as Freud’s hypothesis that people want to believe in gods because they need father figures. I certainly agree with Vitz’ conclusion:
[…] one important conclusion is that in any debate as to the truth of the existence of God, psychology should be irrelevant.