The limitations of the "corporations as persons" argument

Glenn Greenwald at Salon.com has been defending last week's Supreme Court decision that will allow corporations to spend unlimited amounts of money to influence elections. He argues that none of the justices dispute the notion that corporations are "persons" and have First Amendment rights, and he asks several questions to make his point:

Do you believe the FBI has the right to enter and search the offices of the ACLU without probable cause or warrants, and seize whatever they want?

Do they have the right to do that to the offices of labor unions?

How about your local business on the corner which is incorporated?

The only thing stopping them from doing this is the Fourth Amendment. If you believe that corporations have no constitutional rights because they're not persons, what possible objections could you voice if Congress empowered the FBI to do these things?

Can they seize the property (the buildings and cars and bank accounts) of those entities without due process or just compensation? If you believe that corporations have no Constitutional rights, what possible constitutional objections could you have to such laws and actions?

Could Congress pass a law tomorrow providing that any corporation - including non-profit advocacy groups -- which criticize American wars shall be fined $100,000 for each criticism? What possible constitutional objection could you have to that?

The problem, of course, is that while it's perfectly reasonable for corporations and other entities to have all of the protections that he illustrates here, we still don't allow them to vote in elections, run for office, or be appointed to serve as, hmm, let's say, Supreme Court Justices. Just because corporations, labor unions, and other legally recognized entities have certain rights under the law doesn't mean that they should have all the same rights as living, breathing human beings. Is that really so unobvious, Glenn?