Yes, the protection of an innocent life is perhaps where it starts. But where does it go from there? It defines the life in question in a most controversial, unnatural and disrespectful way, showing little or no regard for the women whose pregnancies are what sustain these innocent embryos and fetuses. This is what is meant by the church's woeful neglect of nuance.

Moreover, not all cases of "innocent life" receive the same advocacy from church authorities. The most notorious example of this bias, affecting the greatest number by far of innocent living creatures doomed to die, is the failure to pronounce a robust doctrine of defense of nonhuman animals exploited and killed in the various food industries. A minimal consequence would be to declare an animal-free diet part of  a commendable, even virtuous Christian lifestyle. A stronger, more logical consequence, along the lines of declaring abortion a sin, would be to declare eating animal-sourced foods a complicity in sin.