I see both their points. And I see flaws in their black/white argument.
I don't believe a woman has a right to unilaterally decide to have a child. Such a decision imposes heavy monetary obligations on the father, and often on both of the prospective parents' parents. Deciding to have a child who will not be entirely wanted is not such a good thing. For those who give their unwanted children up for adoption, the foster care system in this country is bankrupt, and foster children are more likely to go to prison than not.
OTOH, I believe a child's life starts at conception. From that point on, there is potential for life. From that point on we are talking about killing.
But if killing an embryo saves the mother's life, sure. My definition of saving a mother's life includes saving a too-young woman, or a rape victim, from having to raise an unwanted child. In many, maybe most, cases a seriously deformed baby will be unwanted.
But my bottom line on this is it is not something for the government to decide.