The question of why was yours, not his, correct? In any case regarding rights which you addressed in
your response to him. The Const does not recognize any rights for the unborn and even the fetal homicide laws do not...each explicitly exempts abortion and allows the woman to kill them. So...no right to life. States are trying to recognize rights for the unborn but that does not supersede the federal status.
As for internationally here's a widespread example,
Article 1
All human beings are born free and equal in dignity and rights. They are endowed with reason and conscience and should act towards one another in a spirit of brotherhood.
So again I wonder what you believe the legal status of person means beyond a label? There are philosophical ways to address it but it seems the focus was on the legal.
I dont mean to be contentious, I've just cut and pasted this stuff so many times I start making my responses shorter and shorter.