Even many pro abortion folks--even our supposed "most pro-abortion president ever"--have explicitly said that they want abortion to be rare, so that is something to build on. Clearly they acknowledge it is not a desirable solution--they recognize there is something sinister in it if they want to make it rare, so the argumentation needs to revolve around discussing if it isn't even more sinister than they recognize it to be--so sinister that we just can't allow it to remain legal any more than other forms of taking human life are legal.
The second reason is to elaborate and respond to some friends who are pro abortion and I've recently discussing the issue with in bits (e.g., on twitter).
So, I'll try to elaborate some rationale supporting abortion w/o simply vilifying or caricaturing in hopes of helping my anti abortion friends understand and empathize with the thinking a bit more, and I'll consequently respond to each position and explain why I can't see it as viable. Doubtless I'll do an imperfect job at both, so I ask for some indulgence and understanding. I know that I, too, am biased despite my attempts at being fair and deliberate.
As I see it currently in my thinking, the abortion debate boils down to basically two issues.
1) When does human life begin?
2) Does all human life have equal dignity and correspondingly demand equal protection?
This is why phrasing the debate in terms of pro life and pro choice is a terrible mistake and has only led to further galvanize irrational people on both sides. So-called "pro choice" people are no more consciously anti-life than "pro life" people are anti choice. We really should just say pro/anti abortion.
Only a true monster would prioritize a mother's whim over the life of an innocent, defenseless human being in her womb. So, pro abortion folks have to believe that it is not a human life in question. I think this applies to the majority of people who'd classify themselves as pro choice.
The reply to this position is surprisingly simple. The consensus in biology tells us that at conception, a new organism is created that, left uninhibited and given natural nourishment, will divide and develop into a recognizable human body, be born, and mature into adulthood. It has all the genetic information that will make it up, so genetically speaking, once conceived, it is fully its own human life. (Would like to highlight that this has absolutely ZERO to do with religion--we're talking about hardcore science.)
For those who think this through and are attached to the pro abortion position, they must fall back on the second issue--a definition of when life deserves to be protected, i.e., what life is worth living and, correspondingly, worth protecting. Put another way, at what point does a human life gain human rights such as the right to life?
Leaving this delineation up for debate is, in my opinion, a truly frightening proposition, for a number of reasons:
1) For a life in the womb, the judgment of whether or not the life is worth living is based on conjecture. Will the parents have the money, time, or even psychological or social capacity to raise the child well? Will the child become a "productive member of society"? And so on.. even if you buy into the idea that some life is not worth living (which is a very debatable idea), to make that judgment on conjecture about the future is dangerous to say the least. The future simply cannot be predicted--to gamble someone else's life on a future prediction is unconscionable. It's no different from those parents who go crazy because they lost everything in some financial disaster and then kill their whole families because they can't imagine how they can continue to provide for them.
2) Even if we could reliably predict the future, it's axiomatic that perspective is everything. Some people can live in and through the most terrible circumstances and still be joyful, content people, while the wealthiest celebrities seem to have a knack for self destruction. Even if an externally dire life situation were likely, that's no indicator at all as to how happy or fulfilled an individual person might be living it. It's just not right to prevent someone even having the chance to have what they'd consider to be a satisfactory or even happy life.
3) We also know that except for a small minority, people tend to have a very strong urge for self-preservation, so given the choice, most people won't kill themselves, even if they are unhappy. So if the vast majority of people won't choose to kill themselves, who are we to kill them preemptively? Seems obvious that we should assume they will, like most people, want to live, even in unfortunate circumstances.
4) <insert other quality of life indicator here> - It all boils down to an essentially completely arbitrary line in the sand as to what constitutes a human life worth protecting, and when you make that line movable based on non-objective criteria, you open yourself up for tragedy like was seen in the 20th century with the many genocides that occurred under the Nazis, the Communists, Rwanda, and elsewhere. And anti abortion folks would indeed also say that the lives taken through abortion is genocide on the grandest scale ever.
In all genocides, someone decides that these certain criteria mean that those who meet that criteria are not fully human and so they can be treated like animals or worse and killed at whim. Under current law that allows abortion on demand, we are saying that we think that parents, sometimes even teenagers, can set those criteria for their children (but only in the womb and usually only to a certain term, oddly enough).
We don't let teenagers vote or drink, but we can let them set criteria for human life worth protecting? We insist that parents educate their children and restrict their choice in regards to their children on a host of other matters (like wearing bike helmets), but we let them decide in the first place if their child's life is worth living? How does that make sense?
Freedom in general and freedom to choose in particular are always constrained in a civilized society. Phrasing the debate in terms of choice is disingenuous; phrasing it in terms of "women's [reproductive] rights" is even more so. It's not about a black and white matter of freedom or choice but whether or not parents should be able to choose if the life of their child is worth living, and given the considerations above--even granting that some human life is not worth life (which for the record I reject)--any reasonable person should see that arbitrarily drawing a line in the sand is an unacceptable option when considering human life and the rights it entails. We have to fix human rights to something more objective, and as noted, that objective thing is biology--we know a human life is genetically fully itself once conceived, and any point after that is an arbitrary judgment related to quality of life, which is simply unacceptable.
So no, pro abortion people are not monsters. I have to believe they just aren't clear thinkers because the reasoning against abortion is simply too strong. I admit it ultimately does boil down to a judgment call considering the various rationales; I just don't see how the other conclusion is viable in the end. To accept the pro abortion position, you have to accept too many unacceptable implications and risk something that is entirely too valuable--human life.