My point exactly: They are not capable.
Again, it isn't particularly meaningful to compare an ability to an inability: We grow up to be able to become declared atheists, but we will never grow up to be able to fly. At least not on our own.
So, I missed it, then--are you saying it is legitimate to tell parents their baby is illiterate? That it cannot drive, or play violin?
There are innumerable things that babies do not or cannot do; if it is not particularly meaningful, why do you seem to insist that it is meaningful to call them atheists?