Re: The line
I would not go so far as to call a fertilized egg a human being. I would call a third-trimester fetus a human being. We can debate where the line goes, both in terms of biology and religion, but there is a line, and it is before the child is born.
Most pro-abortion organizations will not accept this viewpoint. Most Americans do, and most favor neither the abortion-on-demand-anytime view or the abortion-is-a-criminal-act view.