Objections, put it simply, end when more important rights are at stake. Let's imagine a Jehovah's witness parent refusing a minor a blood transfusion - In this cased it should not be allowed. But in the case of abortion, there is no reason to not allow it since it's still a controversial issue. The case you quoted of Muslim women should not be allowed if they endanger the patient's life, and the case of the murderer depends on the jail time and if he can be rehabilitated or not.
And there's the crux of it: "more important rights are at stake"
The more important rights here are that of the living, breathing woman over those of a cluster of cells.
Playing Cluedo with my mum while I was at Uni:
"You did WHAT? With WHO? WHERE???"
