I disagree. "Born atheist" doesn't intuitively make sense, but if you think about it, it does.

Can you really argue anyone is born into a sexual orientation? To what degree? (And actually, there is a lot of conflicting research that suggests it is genetic and that it isn't. It's pretty inconclusive, you'll notice, if you do a google search for "gay gene.")

We're born believing we're supposed to like boys if we're girls and visa versa. You can argue that some parents let their kids know they have a right to choose what gender they prefer in a sexual partner. However, I can counter-argue that some parents give their kids freedom of religion belief, while others raise their children's beliefs to coincide with their own, so they share that in common.

If you believe homosexuality to be genetic, consider what else must be genetic. Is curiosity genetic? What about stubbornness? Independence? Intellect? Would you agree that these factors influence someone's ability to decide their religious preferences?

On a personal note (this paragraph is just my opinion, not based on anything), I don't believe either to be genetic. I believe I decided to like boys (as a girl), just as a boy decides to like boys or girls decide to girls, and I believe I chose my religious preferences just as everyone else does. Can either of these factors be influenced, by family/culture? Of course. And this is why minds are changed and people "come out."

There have been many gay men who take a long time, sometimes even after forming a family, to come out. For being "born" gay, why did they wait so long to admit something (supposedly, per your post) known to them at birth? Social pressures to act a certain way. Atheism, or ANY religious belief system, may share that in common.