Forced birthing and forced abortion cannot be on the same level then. Forced sterilization cannot be compared to putting a human in this world that never asked to be born to begin with. Taking someones reproductive ability away affects only one person while forcing someone to stay pregnant affects her as well as the future child (and possibly father, too). How can you justify forcing someone to give birth when it has far more consequences then forcing an abortion? No matter what your religion or politics may be it can always be agreed upon that human beings are not returnable. The bane of parenthood is that kids are not returnable. To repeat the point from earlier: more often than not people have no business breeding to begin with. Theres a difference between an unplanned pregnancy and the choice to have a child. But the first one is not a good sign of readiness to care for another a person properly nor fitness. Women who get abortions are generally responsible, well-informed individuals that are aware of the negative consequences of having a child at the present time or anytime for that matter. But the reasons most people keep a pregnancy are generally lean towards selfish side. "It will fix me, I can trap my partner, I'll have someone to love me, I like babies, I can't find anything better to do with my life, I'll have power over another person". Not to mention that a person simply should not be reproducing period with such conditions as mental/physical problems, or have unstable lives, or lack financiel means. To be pro-chocie is to support and encourage the former to have kids or get an abortion. But you forget how many people allow "kids to simply happen". We can't just consider forced sterilization (or reversal sterilization) within the context of our current pronatalist culture, but also in the ugly reality that too many people only think with their vagina or dick when making decision to keep a pregnancy. And this has consequences for the mother as well as the future child.
(I'm not necessarily advocating forced abortion/sterilization, but simply considering it in a different perspective that what you typically hear about. Honestly, I doubt that either of them will ever be reality anyways. I'm trying to bring the "abortion debate" in a totally different unapologetic direction.)