Your argument that Freud’s theorization of religion really isn’t pertinent to the metaphysical question of the existence of God (amateriality) is appropriate. To the extent that psychoanalysis belongs to the family of material sciences, Freud really couldn’t have advanced any definitive statement on the existence or non-existence of being outside of the bounded reality of the material universe, which, in any case, is irrelevant if the larger purpose of your analysis is to probe the roots of religious faith as a rational construct grounded in material human experience. In this regard, I’m inclined to stick to Marx’s critique of Feuerbach (or at least my own reading on Marx’s “Theses on Feuerbach”) that the material roots of religious faith are too complex and multifarious to be reduced to a single ultimate explanation, divorced from the particularities of practical/historical human experience (economy, politics, ecology, etc.), rendering Feuerbach’s approach, at most, a partial departure from Hegelian idealism on the transition toward a more robust materialist social theory.
Having said that, I would agree with your conditional hypothesis that it would be inconsistent for an atheist to argue that religious faith constitutes a form of wish-fulfillment without simultaneously acknowledging the same of atheism, provided we acknowledge that such a conclusion takes the Freudian construct of the Oedipus complex as its point of departure. My fault with this argument resides in the capacity of the Freudian theory of religious faith to transcend the limitations inherent in Feuerbach. The Oedipus complex illuminates certain important insights in human psychological development relative to sexual instincts and these are legitimately pertinent to broader examination of neuroses, but I have a problem with the notion that we can wholly reduce the motivations for religious faith or its rejection to the Oedipal account as if it is the universal psychological grounding for every dimension of human social relations, including religion, in every conceivable social context. Epistemologically speaking, this strikes me as a leap of faith in Freudian psychoanalysis that I’m not willing to take.
Further, if the Oedipal account can shed some light on the psychological groundings of both religious faith and atheism (and I am willing to accept your conclusions in this respect), then so what? What are the social implications of, say, the breakdown of familial institutions in the West and the incomplete response of the state to address the effects of such patterns to the acceptance or rejection of religious faith? Such questions seem to be implied as followup social analyses from this psychological theorization.