People rationalize whatever their stance happens to be. Maybe they look at the fetus as an innocent life, while they see soldiers on the ooposite side similar to how we think of self defense. Or, they divide it up in their mind as good and evil, and it is ok to get rid of evil, even kill it.
Abortion in the US has become so political that it also has to do with siding with the side you want to be identified with an accepted by. I know people who say they are pro-life who have had abortions. They would never admit it to their friends at their church. I am talking about people who had pregnancies going very wrong, not just aborting because they didn’t want the baby, they all really wanted to have the baby, all purposely became pregnant. But, they need to believe they are pro-life and need to be accepted in their communities as pro-life. Of course there are people out there who will voice they support some exceptions for abortion, but almost never do they talk about a problem with the fetus, it is always life of the mother or rape and incest. And, even then, look at the nun who was excommunicated a few years ago for helping a woman get an abortion, because the woman’s life was at risk. The church didn’t care. She was already a mother, happy to be pregnant, and had a few other children she had to worry about.