It's not killing someone. A fetus isn't a person.
> I can’t imagine anything LESS scummy than helping save the lives of those babies who are now likely very glad they were born
So would it be ethical to rape someone and force them to give birth? Because the babies would be happy to be born and experiencing life? That's the same logic you're using.
A fetus isn't a person. It's not sentient. It doesn't have hopes and dreams. Personally, I feel guiltier eating pork than having an abortion. Because unlike a fetus, pigs are highly intelligent, social and emotional beings.
On the other hand, a woman is a person. She has the right to control her own body and her own life. If she doesn't want children, she should not be forced to have children. Even if she has sex! Yes, I know that's radical, but I believe that women should be able to have as much sex as they want, with whoever they want, even outside of marriage, without being punished with unwanted children.
I know, and I'm sure you know, that's the real issue. Lots of people are uncomfortable with the concept of consequence-free sex. Christianity, the largest religion in the western world, teaches that sex outside of marriage is wrong. That's why so many people who are against abortion "just happen" to be socially conservative. That's why they "just happen" to be against LGBT as well even though that has fuck-all to do with 'saving babies.' That's why they oppose comprehensive sex education and birth control access, even though that's the most obvious way to reduce unplanned pregnancies.