Really this comes down to sloppy usage of words. You said the phrase yourself: "juridical people." You need that qualifier on it, "juridical," to distinguish from actual human beings. Because they're not the same. "Corporations are people" -> corporations are legal entities that share some of the same rights, privileges, and responsibilities as human beings. "Corporations aren't people" -> corporations are a distinct concept from human beings, including ethically and legally.

Legally, the argument comes down to how precise you're being. Is there an implied qualifier? Is the statement meant to convey that corporations are legally the same as natural persons (they aren't) or just that they are some sort of legal entity? And the whole dispute here is because people are interpreting it differently.

To rephrase the comment some replies above: "Because corporations aren't natural people."

All the discussion about corporate personhood is off the mark, because corporate personhood only means that corporations have some of the rights that natural persons have, and voting is not generally among them. Although apparently it is in one town in Delaware.