I believe it is fine for people to believe no one should be killed because there are other ways to deal with extreme criminals (life in prison, justice and the law is upheld), that is their choice and belief (Absolute pro-life). But, it is morally wrong to believe individuals should have a sole right to terminate anyone's life for any reason. Killing someone in legitimate self-defense is one reason why someone would morally just to kill someone else, in a just war as a soldier would be another case. It is never permitted to kill innocents.
Why innocent children should have to pay with their life for the so-called "mistakes" of others is beyond my comprehension.
Like you, I cannot fathom why anyone would be so selfish as to kill a baby for mere convenience. The problem is that the pro-abortion crowd has done a far better P.R. job than we have.