The basic disagreement between abolitionist and pro-life thinking comes in the foundations of our understand and approach to abortion. Pro-lifers will say things like the following:
“The reason I believe this is not because of my Christianity; science supports what I’m saying.”
“I can produce good legislation that protects children without appealing to Christianity or God’s higher law.”
The particular issue may vary, but in its foundation, pro-life rhetoric and strategy will leave the word of God out of the discussion, trying to meet secularists on some form of “common ground.”
The trouble is, for a biblical thinker, when you leave Christianity out of the argument, you’re leaving out the very foundation of rational thought. Jesus Christ, the incarnate Word who spoke the universe (and therefore scientific processes etc.) into existence, said the following about Himself: “I am the way, and the truth, and the life. No one comes to the Father except through me.” (Jhn 14:6) His words are emphatic; all truth (and life) ultimately flows out of Jesus, so you cannot arrive at a rational understanding of anything if your knowledge is generated in a way that departs from the foundation of truth Himself.
Answers in Genesis does a lot of good work in this regard; Ken Ham and friends will talk about the fact that darwinists can believe in many true things, but when you trace back their reason for believing these ideas, it’s because they are inconsistently drawing from the Christian worldview. Conversely, many Christians will try to argue with Darwinists by ”meeting in the middle” — stepping out of the Christian worldview to debate through “reason built on common ground.” These Christians do not realize that the alleged common ground is a man or creation-centered philosophy (e.g. materialism) which tries to derive truth by presupposing that the foundation of truth (God) is either unnecessary in epistemology (knowledge building), or a flat-out lie.
So in the origins debate, there are three schools of thought — the secularists (darwinists), the syncretists (intelligent design, old earth creationism etc.), and the biblicists (creationists). The syncretists can present a tempting offer to Christians, because they can appear to produce rational arguments by meeting the secularists on common ground; however in doing so they abandon the foundation of scripture and biblical thinking. It is ultimately the biblicists who hold a consistently logical, rational worldview by openly and unashamedly building everything on the foundation of truth, Jesus Christ.
In the same way, during the abolition of slavery, there were three schools of thought in terms of how to address that issue — the secularists / compromised Christians (pro-slavery), the syncretists (colonizationists), and the biblicists (the abolitionists). The abolitionists were “radicals” who were constantly being criticized by the colonizationists for their unwillingness to leave the gospel and the word of God out of the discussion. Yet they refused to be ashamed of their biblical foundation, and it was ultimately the biblicists who got the job done — because slavery is a sin issue, Jesus Christ actually is Truth, and the gospel actually is the only remedy to sin.
In the same way, during the abolition of abortion, there are now three schools of thought — the secularists (pro-choicers), the syncretists (pro-lifers), and the biblicists (abolitionists). Like the abolitionists who fought the colonizationist movement, we abolitionists believe that the single greatest thing that is keeping abortion legal is not the pro-choice movement, but rather the pro-life movement. It’s the same strategy that Satan has used for ages; by presenting a syncretistic answer to abortion, well-meaning Christians will leave the word of God out of the discussion, effectively leaving out the cure.
The five tenets of abolitionism outlined above develop five areas where the pro-life movement abandons the biblical worldview. To provide just one brief example however, many pro-lifers assume the premise that all innocent human beings have the right to life; not everyone agrees with that. Consistent darwinists for example don’t view a categorical difference between humans and animals; the foundational premise of their moral code is the idea that might makes right — survival of the fittest. If a society of human animals finds survival value in working together, then a code of acceptable behavior that protects life may be present; however there is nothing inherent to the nature of humanity which says that their atoms and cells must not be changed in their arrangement by a knife or blunt object etc.; death is amoral, a simple fact of the material state of the universe.
Christianity alone is able to produce human worth, because Christianity alone is actually true. Other religions try, but the reasons for believing in them are simply illogical, arbitrary, and often self-contradictory; and ultimately they all devolve into humanism. Biblical Christianity on the other hand presents a robust worldview that explains the whole order of creation that we see around us, past, present and future. As mentioned above, human beings have rights because we are created in the image of God, so to attack a human, you are attacking God, and by extension all of creation under His and man’s authority (Gen 9:6).
When the pro-life movement leaves the biblical worldview and tries to argue from a place of common ground, they are leaving the foundation of truth, and their arguments become just as arbitrary and illogical as those of the pro-choice movement. As a result, pro-life legislation is foundationally pro-choice, regulating the conditions under which parents may choose to murder their children.