Mind boggling, isn't it? I guess "saving" the life of the mother AND sperm donor far exceeds any child's right to exist... sick, sicker, sickest!
It would be true if the alternative of the birth of the child would be the death of the parents. However, if life is at risk, only the mother's life is at risk.
It's an example of one of those arguments where one side isn't able to really put forth a good argument, so they start shouting. They hope to replace logic with volume.
Shalom.