I am pro-life because I am a Christian
I used to be a hypocrite, a liar and a coward regarding the reason I oppose abortion. I still sin in many ways, but this is one area where I have repented of the sins of my youth.
In my younger days, when I was challenged on my pro-life views by people who say I just want to "force my religion" on people, I would say no, this is not about religion. This is about human rights. This is about equality under the law. This is about defending the oppressed from being killed. My arguments are purely secular arguments. While these are all valid reasons to oppose abortion and they are good arguments to use against it, I hid the real motivation for my opposition to abortion because I lacked the faith, courage, and honesty to say what I actually believed. To some extent, I had deceived myself into believing my own lies.
The reason abortion is wrong is not for secular "human rights" reasons. The reason abortion is wrong, and the reason all murder is wrong, is because human beings are made in the image of God. Killing a human being, then, is an affront to something that bears the image of our Creator. God calls us to defend the innocent and rescue those being led away to death. That is why anti-abortion groups are almost exclusively Christian.
When Christian Citizens for Life was being formed, the people at those early meetings wanted it to be explicit that we were a Christian group. (I actually was not at that particular meeting when the name was chosen, so I cannot take credit for this.) This is because opposing abortion is the way we are called to serve God. We know from places such as Leviticus 20 how much God hates child sacrifice, and how He commands we oppose it. What is abortion but the modern-day version of Molech worship, except to the false god of "reproductive choice" instead of a dead stone idol?
No, this does not mean that I believe that every aspect of the Old Testament Law (much of which was fulfilled by the death of Jesus Christ) should be in our criminal code. I actually have a very strong libertarian streak and I do not want government micromanaging where we can live, what we can eat and drink, or how we run our businesses. For the most part, we should be free to make our own choices.
But when it comes to things like abortion, rape and murder - things that violate the rights of other human beings - I am unapologetic that the reason I want these things to be illegal is because God commands that they should be illegal. I am not seeking to impose my personal values on anyone. I am instead submitting to the authority of the God who created me and then died for me when I sinned against Him.