Upchurch
Papa Funkosophy
It's the First Amendment.No, the constitution doesn't say "no no".
People have moral intuitions. Those intuitions are necessarily informed by the cultural traditions they are raised in. You have an intuition that these are "not-yet-beings", other people's intuitions say different.
I was raised in a cultural setting that would likely go with "God puts the soul in the little-bitty babies the moment the sperm touches the egg". I was capable of questioning my indoctrination with skepticism and critical thought. Technically, everyone is capable of it, though few seem to make the effort.
Historically, the concept comes from the Catholic religion and was adopted quite quickly, ironically enough, by evangelical sects of Christianity. The concept that the early zygote or embryo is anything equivalent personhood was based solely on the idea that it has a soul. Otherwise, there is nothing being-like about it. Prior to that, a good number of religions and traditions held that the fetus was a person once the quickening had happened, and not before.

off. The actual philosophy behind those self-evident truths were argued and debated and took quite a while to be understood before actually being adopted. If anything, those "truths" are a great example of reason and rational thought, especially the parts deconstructing the sovereignty of royal birthright.