converting back unto theism - yes it's true.

[Tiberius]

Atheists often seem to accuse "re-converters" of not being atheists in the first place, as if atheism is some final end-point of a one-way journey that cannot possibly be reversed. You get to atheism by rejection of theism, and you can get to theism by a rejection of atheism. It might be true that a previous rejection was made for the wrong reasons, but that doesn't mean that an atheist that reconverts to theism was "never an atheist".

I think the argument does have some merit with a few choice examples though, which probably explains why so many think this is a good argument. People like Kirk Cameron, Lee Strobel, etc could fall in this category easily, by the lack of understanding they show about atheism. However, as with all arguments that have some basis in a personal experience, I wouldn't use it.