LOL, which is the point of course.
The point is we have one party that welcomes us, and another party with a large, powerful, vocal faction that thinks we are immoral scum, that our kind isn't even qualified to hold office, isn't even worthy of citizenship.
Other than that basic fact, there is ZERO ideological reason on any other issue why an atheist should necessarily vote Democrat.
IOW, if atheists vote Democrat, it is because they are pushed away from Republicans, not naturally attracted to liberalism.