There are several who consider themselves (or, in the case of Antony Flew, are considered by others) to be in a category of “former atheists.” This, it would seem, gives a bit of “street cred” to their arguments that atheism is wrong and Christianity is the right path. After all, they were once “misguided” and now shown the light.
But how many of these alleged “former atheists” were truly atheists? In the end, it doesn’t really matter since the argument that christianity is true since one or more atheists have recanted is fallacious to begin with. It assumes true the premise that it is possible for a person to be deluded (from their perspective, aren’t they arguing that the atheist was deluded?) but doesn’t demonstrate which is actually the delusion: the atheist or the theist.
If we were to accept that were something to “wake up from” like a dream, then whichever condition had more adult converts would be the more likely. My money, in that case, would be on atheism. But even this line of argumentation would have flaws.
The “former atheist” argument, however, probably isn’t geared so much an attempt to show why theism is more likely but, rather, an attempt by apologists to capitalize on the enormous credibility former theists who now embrace atheism have had. Books by Dan Barker and John W. Loftus have had a profound impact on believers who then begin questioning their “faith.” Leadership within the various superstitions of Christianity want this for themselves and promote their own “former” and “deconverted” stories.
Antony Flew is a much touted case, but his conversion really isn’t that significant when examined closely. As a philosopher, he still rejects the cosmological and ontological arguments for a god favored by many theists. Indeed his philosophical views are that of a deistic perspective and certainly not a Christian one, so for all the “nah nah nana nur nur” generated by Christian apologists, Flews change in philosophy isn’t all that significant or notable.
Two popular Christian apologists and alleged former atheists are Alister McGrath and Kirk Cameron. Both alleged in their adult writings and talks that they were atheists up to their teen years but converted to Christianity as young adults. The gist of it is: “because I was a teenage atheist like you, and now I’ve seen the “light,” you should consider your own atheism as wrong,” or “you’re just a confused kid, when you’re an adult you’ll naturally see “the truth”" and other fallacious assumptions.
The reality is that apologists want the credential of having “once been” where their critics are.