In my experience it’s less common but not crazy rare. Atheism often comes with experience challenging society’s expectations and that means you’re usually more open minded. But these opinions aren’t inherently tied to religion. I’ve met people who argue their pro choice stance from a Christian perspective (life begins at first breath is in the Bible) and I’ve seen atheists claim that distinct genetics mean that fetuses are equally alive. Homosexuality is less easy for side switching as it’s not explicitly permitted in the Christian Bible, and opposition to it on science grounds are harder but it tends to come down to unexamined discomfort and the reasoning comes later. For atheists it will be related to the biological imperative to reproduce or eugenics and social contagion rhetoric.
Also there’s the new atheists who are basically all Alt right bigots