Some lazy stereotyping. And possibly some mixing up of Christianity with Creationism.
Isn’t that the point of the cartoon? That if you fulfill the roles depicted (indoctrinating children, promoting creationism over science) then you suck at religion – therefore, if you don’t do those things then although you may be religious, but you don’t suck at religion.
It’s worth bearing in mind that The Oatmeal is based in the US, where they do have proper scary right-wing Christian nut-jobs (in some states they’re trying to prevent birth control from being available, never mind abortion, gays are banned from being in the Scouts, etc).