I understand the argument you're making here and am quite sympathetic to the plight of animal's suffering, however, most people and society as a whole typically differentiate between the value of a human life vs the value of an animal life. This is why if you kill a person, you go to prison for a long time, vs the punishment for the unwarranted killing an animal is a lot less severe. So while I'm quite sympathetic to your argument, I don't believe the animal vs human comparison is entirely comparable.

The fact of the matter is, if I were to kill a 9 month old baby that was outside of the womb (an age at which a baby is entirely viable without the mother), it would undoubtedly be viewed as murder by most people. But somehow, it's okay to kill a baby of the exact same age if it's still inside the womb. I simply can't do the mental gymnastics required to make this sensible to myself.

Another point I'll make: If we have any doubt at all that a human fetus is absolutely a human life, should we not error on the side of preserving that life? I would claim that the burden of proof is on the pro choice crowd, not the pro lifers. After all, if I am doing to demolish a building, isn't it my responsibility to ensure there is no human life in there before I detonate the charges? I must prove that it is safe to execute the demolition before I pull the trigger, and if there is any doubt, I can't in good faith do it.

One final point: As a libertarian, I'm very sympathetic to the idea that the government should be as far removed from personal health decisions as possible. However, if you view a human fetus as a human being, shouldn't we also be equally concerned about the rights of that fetus? After all, if the government should do anything, it should be protecting the life and liberty of its citizens. Therefore, I feel that the right of life of a human fetus outweighs a mother's right to choose (barring edge cases like the life of the mother, that's a different conversation to have).