Indeed, that would push more people away.
However, many women feel like they really don't have a choice, or don't have any support.
I don't think being pro-life = standing and screaming. Silent witness and prayer helps as well. As does giving people information that support is out there (birthrite.org), as does educating people as to when different biological events occur.
You do realize that there are pro-life atheists, right?
The writings of a pro-life atheist (Nat Hentoff) helped me along the path to a pro-life position.