This is one of those interesting things. If we accept OP's premise for the sake of argument... then what does that really change? Society accepts that people can be lawfully killed on purpose given the "right" circumstances (e.g.: criminal punishment, war combat, equivocal self-defense). We generally don't like it, but we do fundamentally accept that human life is on the negotiating table when justified.

That's what irks me about the murder label. We already willfully choose to end human lives, irrevocably destroying a vast collection of lived experiences and social connections in the process. What is destroyed when an unborn child dies? A life which knows nobody, understands nothing, and thinks/feels at best at a level no more complex than animals which we routinely slaughter without a second thought. One might argue that the life itself contains some unknowable potential for these things, but that theoretical future potential comes at the price of the mother's current potential and freedoms.

The way I see it, the position is inherently precious. It fears the label of murder without caring to consider why the label exists. A philosophy so myopically focused on keeping one's own moral hands clean that the term "second order consequence" may as well be written in hieroglyphics.

Self defense is never murder.

Agreed.