I would agree with you that so-called believers have not done enough to prevent abortion, absolutely. But I would argue the percentage of practical atheists is higher than 10% consisting of liberal Christians, agnostics, and the like. I believe the 10% figure is more likely those who openly profess themselves Atheists. And even the 10% figure is probably a bit high because I don't truly believe all Atheists are faithful to their atheist religion when the chips are down.
Well, I don’t want to go down the rabbit hole of trying to divine someone’s real beliefs since it is a futile game. And conveniently labeling those who do not share all the tenets of what you believe to be the rightful definition of Christianity is also a mug’s game. It is a little too convenient to reject a person’s faith just because they don’t always adhere to the teachings you subscribe to.
When you look at surveys of behavior like viewing pornography, divorce, and downloading illegal copies of music (even Christian music!) then the behavior of “Bible-believing” Christians is not that much different from the rest of the Christian community. (The surveys can be found via Google). So why should they be any different when if comes to abortion? I think that you will agree that even the most sincere of Christians is capable of acting selfishly at times, and if nothing else, abortion is a selfish act.