Sorry guys, but I was pro-life long before I started going to church or even became a Republican. I became a parent, and as I held my beautiful daughter I realized that I coud never support the killing of an innocent viable human being.
Most atheists are political liberals, and that means most of them do not believe that human life has its own intrinsic value. It's left up to the individual to decide if they're carrying a baby or a fetus. A baby has value. A fetus is worthless to the point of being treated as something less than human. The fetus has simply been dehumanized by the law, treated as a non-person until the baby is given a name. A non-person can't be murdered, and this loophole in the law makes it open season on otherwise viable humans.
In the Atheist world view, God has been eliminated and the human being has become God's replacement, holding power over life and death based on a person's whims.
Destroying the egg of a bald eagle carries the fine of 5000.00 plus jail time:
https://www.dividedstates.com/abortion-eagle%e2%80%99s-egg-vs-human-fetus/
An egg is not an eagle. It has the potential to hatch as an eagle. Yet the egg is assigned more value than a potential live person.
There is something seriously wrong with a society that places less value on a human than on a bird, and labels pro-humans "extremists".