I think an anti-abortion extremist is anyone who does or advocates violence against the other side. Is there any equivalent to that on our side? I could see the forced-birth or hypothetical forced-abortion people as extremist, too - being confronted by an actual living person and making them do what you tell them by force is pretty extreme.

Someone who just thinks abortion is murder, and wants to legislate that - well, I think they're massively misguided, anti-woman & wrong, but their position isn't that extreme given the cultural context, I guess. It's conservative, but it's not way out in right field.