"Corporations are people" is irrelevant to "Citizens United" and other federal-law cases -- just read the case's name!
The phrase "corporations are people" deliberately conjures up images of huge money-grubbing businesses that don't care about people, getting favors from a government that cares more about them than people. It's widely known to come from from early, "Gilded Age" pro-business interpretations of the 14th Amendment. And yet the very name of the "Citizens United" case should be a giveaway that the freedom of non-profit groups of citizens, advocating about political issues, was at stake in the case. Do those who scoff at Citizens United, for supposedly saying corporations are people, really believe that civil rights groups, women's groups, antiwar groups, veterans' groups, and religious groups, have no Constitutional rights?
The second half of the case's name, "v. Federal Election Commission", is a big clue that 14th Amendment case law about "persons" has nothing to do with it. The part of the 14th Amendment about persons and rights, Section 1, solely restricts what states can do to people or "persons". It reads:
All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the state wherein they reside. No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any state deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.
But the First Amendment, which works directly on the federal government, and indirectly on states through the 14th Amendment, focuses on prohibiting the government from violating freedom of speech, press, or religion, with absolutely no exceptions concerning who or what is speaking, publishing, etc.
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; ...
There is a reference to "the people" in the second half of it:
"... or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances."
Justice Kennedy's majority opinion in Citizens United does not say corporations are people. Instead it points out that the First Amendment does not make exceptions for who is doing the speaking or publishing; that all effective speech costs money, and that an argument that "corporations aren't natural persons" is not wrong, but irrelevant to the First Amendment.
Joe Albanese pointed out this crucial but apparently never-noticed distinction today, reveling in the irony of Ben & Jerry's using its free-speech rights to argue against corporations having free-speech rights, in "Is Big Ice Cream Trying to Hijack Our Democracy?" Former Federal Election Commission member Brad Smith says more about groups' free speech rights, and another threat to them, in "Tester’s assault on corporate rights is an assault on people’s rights."
I wish people would read the case opinion before criticizing it, but if you don't do that, you could at least read the case's name and the most important sentence in our Constitution.