if atheists truly believed in science, they would do what science predicts to be optimal for themselves and for their group, and have as many kids as possible.
I don't see how that's optimal for them and their group at all. Are you assuming that all atheists want their genes or ideologies to live on?
I guess my point here is that atheists run afoul of the basic principle that there is no amount of knowledge about gun mechanics that will protect you if you shoot yourself in the head.
You're assuming that there is something wrong about being shot in the head.