> Giving a corporation personhood does not give the corporation rights as much as does take away rights from those who interact with that corporation.

I think you are (aside from any debate about your basic position) conflating juridical personhood, which is the issue here, with Constitutional (under, e.g., the 5th and 14th Amendments, and thus applying to rights within the scope of liberty addressed by those Amendments) personhood, as at issue in Citizens United, which are different concepts.

Juridical personhood is a defining feature of corporations, making them subjects of law that can, for instance, be sued.