This. But most people don't see it that way, so it's a question of "when life begins" to most of them.

At the end of the day we assign different value to different lives and most people just don't want to admit it. Which still leaves it a contentious issue because now it's a question of where's the line where it's life is valuable enough to be protected instead of whether or not it is life. If one thing's clear it's that people disagree on where it should be.