Additionally, many people constantly talk about wanting a separation of church and state. If your religious views are entirely separate, there is no justification for denying abortions to consenting adults.
There are atheists and agnostics who are firmly pro-life. Also, when I talk to people about the subject, it's very rare that religion comes up on either side. It comes down to what you consider life, and that differs from person to person despite religious affiliation.
Personally, I am pro-choice. I used to say that I'm morally against it, but legally pro-choice, but I think that's a bit condescending and unfair. It's extremely easy for me to pretend it's some moral argument when I run zero risk of ever getting pregnant. I never have to worry about a broken condom, a rape or ineffective birth control prescription resulting in a tiny life growing in my abdomen.
I'm glad abortion is a legal option. I can't imagine how much worse off this country would be if every unwanted pregnancy bore a child which would eventually become an adult. And, while it sickens me to hear that there are people like Kacey Jordan who have had four abortions, it also sickens me to imagine she didn't have them. This country is already full of neglected and abused children who'll never get a fair shot at life. To mandate the expansion of that seems downright evil.