I'm jumping into this conversation reluctantly, knowing full well how much of a powder keg this topic can be. But I do have some thoughts on this subject and I think the best way to develop thoughts is to air them out and kick 'em around a bit.
Just to get this out of the way, let me first say that I do not agree with anything the author of the OP's article said. Roy Moore is a gross person and his defense by Republicans is damning and pathetic.
I consider myself a fairly progressive person. I am from Texas. Many, many of my friends and family are conservative. Some (a lot) of them are the obnoxious Fox News-Breitbart kind of conservative, but others are thoughtful, intelligent, and reasonable. I also come from a religious (Christian) background, though I certainly don't identify as an "evangelical", socially or theologically.
I do consider myself to be "pro life" in the philosophical sense that human life is one of the only things that has true, inherent value. To borrow Christian terminology, humans are "made in the image of God". Because of this, I am opposed to the death penalty, to torture, to most forms of violence, and to anything that degrades or otherwise dishonors a person's dignity and integrity. Further, I do support welfare and anti-poverty programs, sex education, birth control, gun control regulation, foreign aid and philanthropy, environmentalism and efforts to curb global warming, etc. All of these things are, I believe, consistent with a true pro-life ethic.
I find that progressives are in many ways pro-life as well. In their support for and opposition of many of the things I listed above, for example. However, on the topic of abortion progressives veer away from a pro-life stance and into a pro-liberty stance, which I find interesting (conservatives do the opposite, departing from their typical pro-liberty stance into a pro-regulation one).
To someone who has a strong pro-life ethic as I've described above, abortion is viewed as a violation of another person's inherent dignity and worth (here I am talking only about "elective" abortions, not ones that are deemed necessary for medical reasons as other users in this thread have discussed). You may argue that we don't know whether or not a fetus is a person ("scientifically or legally", as if those were the only two qualifications that bear any weight in the evaluation of a person's worth) and that it is therefore a decision that must be free to made to each individual person according to his or her conscience.
However, we know for certain that a dog, for example, is not a person, and yet we certainly do not allow people to treat a dog in accordance with his or her conscience. I often see more concern given for the welfare of animals and the protection of animal life from progressives than I do for human life. So the personhood of a fetus doesn't really seem to be the factor here. If someone killed a puppy because they decided that raising a dog would sacrifice too much of their own personal autonomy or liberty, we would not praise them as a champion of liberal values but rather (rightly) condemn them for cruelty.
If you object that a puppy is different than a fetus because a fetus is not "viable" outside of the womb, then imagine instead that a puppy comes to you severely malnourished and injured to the point of being near death, so that it is not "viable" without your immediate care. You could let him convalesce in your home by feeding him a few scraps from your dinner table, or you could throw him out the back door. The moral choice here is obvious: why has it become so murky when we begin to consider a human life instead?
I am aware that my facile analogy is flawed, but let me pose two questions: If you believe that abortion is not termination of a human life on the grounds that a fetus is not a human life, have you perhaps considered that our society has worked really hard to make itself believe that so that we are able to sleep at night with the decisions we make to preserve our sacred values of individualism and personal autonomy, even if they come at the cost of human life?
And can you understand why for someone who does believe that a fetus is a human life (which is not so far-fetched) abortion is considered such a morally offensive act?