Fallacious Reasoning in Anti-Abortion Argument (?)

P1. It is wrong to kill innocent humans.

P2. The unborn are innocent humans.

From (P1) and (P2), it is wrong to kill the unborn.

P1) It is morally wrong to kill innocent humans.

P2) The unborn are innocent humans.

C) It is wrong to kill the unborn.

This is a formally valid argument. It follows that, should we not kill innocent humans, given that the unborn are part of that category, we should not kill them. However, it is rationally unpersuasive because its terms are not adequately defined. 'Innocent' could refer to lack of guilt, or it could refer to purity of mind (almost like naivety). Without defining terms, we could easily create a misleading argument (no one would disagree it is wrong to, say, apply the death penalty - kill - a legally innocent person, but it does not follow that 'naivety' should be treated the same way).

Next, it is questionable as to whether the unborn can be 'killed'. Killing requires taking a life - but the unborn arguably  do not  have life, or are not  viably alive in the sense that they can live outside of the body of another. Rather, they depend on the mother and  her  body to function. For instance, a foetus, where the lungs do not work. If this cannot be demonstrated the argument becomes far less effective at conveying its point.

This is absolutely a valid argument. It's a typical modus ponens syllogism. It seems to me an even simpler formulation of it that would be more recognizable to all who have done logic 101 is

1) All innocent human life has intrinsic value. (Obviously innocent human life is to be protected, so we don't need to get into silly red herring debates about the death penalty etc).

2) Unborn human fetuses is human life. (This is a scientific fact).

3) Therefore unborn human fetuses have intrinsic value. (Follows from 1 and 2).

Obviously this is where the debate was during the time of Roe v Wade, and we didn't have the technology we did today, and the pro abortion side actually convinced several courts that a human fetus was nothing more than a "blob of tissue" until near the end of pregnancy when it then formed into a human. Today we know none of that is true.

Today's debate is a bit different, where the pro-life side has won all of the scientific debates, that is they are no longer even in question. The human fetus is a human, and it is not  just a blob.

The last tactic remaining for the pro-abortion side is to try to make bizarre distinctions between a "person" and a "human", and to set up arbitrary benchmarks where a human becomes a "person", some bench mark that they will assert is valuable in their mind (say the full development of the cerebral cortex). They then argue if the human has not met that benchmark, it must be ok to kill them. 

Obvious questions arise from such a position, such as "if someone's cerebral cortex is more developed than mine, are they more of a human than I am?" or "is it ok to kill humans who have a degraded cerebral cortex, maybe if not kill them, use them as a cattle or something?", "Are people with a more developed cerebral cortex superior persons?", and the most fundamental question is "Why isn't a human a 'person' if they don't meet your benchmark, and further, why does that make it ok to kill them?"

For me, that just does not work as an argument at all, but obviously for them, it does.

Great question though.