Being outbred by the religious

[Esquilax]

Our numbers won't increase because we're more fertile. They wil increase because we make more sense and we're no longer silent and invisible.

This contradicts the premise of the OP: "The reality of the planet is that most people retain the religious beliefs of their parents."

Most do: those that don't will find atheism a far more viable option for self-identification if there is a visible public persona for atheism that isn't, say, dominated by the religious caricature of the easily offended, miserable and litigious sinner.

Moreover, you're ignoring the reason that most people retain their parent's beliefs; they aren't exposed to opposing ideas in sufficient strength and presentation to make other options seem worthy of consideration. This has already changed so much due to the internet, we're just trying to help it along.