In Mere Christianity C.S. Lewis said:
"It may be a great advance in knowledge not to believe in witches. There is no moral advance in not executing them when you don't think they are there. You wouldn't call a man humane for ceasing to set mouse-traps if he did so because he believed there were no mice in the house."
I have long thought there was something very wrong with this. There is a moral flaw that makes people willing to believe that their problems must be someone's fault in the absense of evidence, that violence is the answer in the absense of such evidence, and that strange, different, unpopular people are likely to be evil. Even in the presense of such beliefs, it is a moral flaw that will cause one to lead the mob that does the killing.
Some Aztecs believed that human sacrifice was required to keep the world going, that humans would get nothing good from the gods without it. Does this automatically acquit them of charges of murder, if they came to sincerely believe it? Doesn't C.S. Lewis talk about this elsewhere, perhaps in The Great Divorce? Don't misunderstand, I mean only what I say, I wouldn't be surprised to hear he spoke against abortion, and never mentioned the case of rape. Many people do.
Now suppose a high school student is raped. In theory she could finish high school while carrying the child, perhaps taking a few days off from school immediately before and after the birth. In practice this would require more strength than most of us possess. There is the sheerly physical effort of carrying around the foetus and embryonic fluid, there is the sickness that often comes along with it, there is the fact that everyone (children and adults) will treat her differently (especially in a religiously conservative area), and there is even the fact that after having gone through so much the mother might end up dropping out of school to keep the baby born nine months later - a baby she is not mature enough to raise, a baby possibly doomed to a life of poverty and want along with the mother. Or perhaps she doesn't live in the United States - even in countries where abortion is illegal the adoption system often doesn't work.
Suppose the pregnancy is discovered when she misses a period, a few weeks after the rape. Someone who opposes abortion under all circumstances might tell her she must bear it to term at all costs, otherwise she is a murderer. This person sincerly believes that the small clump of cells with no brain yet has a soul, and is human, and has human rights. Even if you disagree, their opposition follows from their premises. Does this mean that while we who disagree may accuse them of error, we must not impute a moral flaw this person based on their demand? Does it matter that only for a few generations has this been a focus for any large religious denomination, and that for centuries religous philosphers spoke of quickening, and the time when human features developed? How about comparing Old Testament penalties for accidental homicide to penalties for causing a miscarriage?
Please don't misinterpret any of these. I'm not comparing abortion or opposing abortion to human sacrifice or killing witches, I'm asking if people can ever be blamed for accepting a premise that leads to an inhumane conclusion, and then being comfortable with that conclusion and not vigorously examining the premise. I realize this sounds harsh when I explain it clearly, but I don't know how to change that. It's also harsh to accuse people of murder and supporting murder.