“Being a kofer is against halacha – thus being a liberal, as defined colloquially, is against halacha.”
If your colloquial definition of a liberal is “one who supports frivolous abortion” then yes. As you can see, many don’t hold of that definition. Being pro-life is more of a litmus test for the right than being pro-choice is for the left. If ~50% of the country is liberal (it’s actually probably more because their side has a not-voting problem), and more than half the country supports greater regulation on abortion, then it just doesn’t add up. We live in a country where the party platforms are not always fully in line with the voters thanks to special interest groups. Could it be that just like people here vote republican despite disagreeing on gun control, many people vote democrat despite disagreeing on abortion?