What exactly does religion have to do with this issue? Whether or not it should be legal to kill a human being for no better reason than convenience doesn't strike me as a religious issue. Do you see other laws with regard to killing - murder, manslaugter, etc as religious issues as well?
I don't think that the person meant religion, but rather, they meant ethics. Hume did not believe in an absolute right or wrong, rather, it is an emotive matter. Personally, I believe that ethics is a societal construction and inculcation, but that is another issue. Abortion is an ethical issue, and thus many people rely on their emotional intuition... and may fail to acknowledge exceptional cases and the impact that a state ban on abortion would have.
People who are entirely pro-life seem to believe that killing is wrong under most circumstances (with the exception of having the child being a threat to the mother), even in the case of rape or incest. I am entirely against this. If a woman is raped by several men in a terrifying experience, I don't understand why she must live with the experience growing in her belly for nine more months so that she can give it up for adoption. It just isn't right, it is like condemning her for having female organs.
I understand that the example I have given is a grotesque and less likely situation... but I believe it should be the woman's choice. I do not condone the use of abortion as a contraceptive form, but I think banning abortion entirely would only make those who actually need the abortion suffer miserably.
And even if a woman was able to give the baby up for adoption, how about the children who are not adopted? I don't think it is fair to abandon hardship and responsibility, only to transfer it to a child you will never have to face.
If we want to decrease the number of unwanted pregnancies, and thus abortions, we should increase education and awareness (in both men and women) and availability of local clinics with access to contraceptives.
That is all..
Btw, has anyone read the bit in Freakonomics, about the impact Roe v. Wade has had on the crime rate?