The question is what is the liberal position? For instance that a fetus doesn't have brain waves until the third trimester is a scientific fact, not a theological question... So we could argue when does personhood start, which is the real question...
My guess given the facts is about the 20-21st week of gestation. Some put it as early as the 18th, other as late as the 25th, but these are the limits... Before, there is not any person... After, there is...
The fact of the matter is that the extreme position taken is theologically based, and by and large is the peoduct of the original sin doctrine.
Instead of fighting a losing fight, you better try to see what are the fights that can be won... Third trimester abortions obviously are the ones that are problematic... Even late second trimester... And on this, a lot of people would agree to limits (probably a majority)...
But trying to ban contraception and first trimester abortions isn't going to happen. Because people see the difference, even if doctrinaires don't...
'Original sin' is nonsense, IMO. But the fact remains that elective abortion ends a human life.