No. A corporation is not a person by any commonsense definition, most specifically because it is not a citizen.
Over the past few years the right has rationalized that illegal immigrants and terror suspects have no rights because they are not citizens. We are, as the argument goes, therefore free to expel, imprison and interrogate them as we see fit.
Consistently applying this rationale to corporations means that the only rights they should have are the rights that are bestowed upon them by the laws that govern their creation and operation. By any commonsense definition corporations are not people and the government is free to dictate restrictions on their behavior, which it still does in excruciating detail.
Unlike citizens, corporations are not mentioned in the Constitution. Nothing in the Constitution says that a corporation is a person. They are given no rights by the Constitution. A slave (euphemistically called a person "bound to Service for a Term of Years") is worth three-fifths of a person. A corporation? Zero.
If fact, corporations as they exist today did not exist at the time the Constitution was written. They did not become "artificial persons" that "possess individuality and immortality" until 1819 in another notorious Supreme Court decision.
Corporations exist solely to allow individuals to band together to avoid personal responsibility for collective actions. In particular, corporations are formed (in preference to partnerships) to avoid personal financial liability in the event of bankruptcy or other legal responsibility. This isn't evil or bad, it's necessary to run a business. But it's the reason why corporations aren't people.
As long as the officers of a corporation don't mix personal and corporate finances, and commit no crimes, they can run a company into bankruptcy and walk away without personal consequences. For example: let's say the officers of MegaMaint, a large building maintenance services corporation, build a new building with fancy offices for themselves and a fleet of nice new trucks, all with big loans from a bank. The building -- built by the lowest bidder -- has huge cost overruns, is poorly constructed and eventually collapses before completion. The trucks all break down -- lowest bidder again. MegaMaint goes bankrupt. The assets of the company are liquidated and the bank gets almost nothing. The bank goes after building contractor and the truck company, but they declare bankruptcy and their corporate officers skip out as well.
Now let's say that Jim is a small businessman who runs a sole-proprietor window-cleaning business. He doesn't have the money or wherewithal to hire a lawyer and set up a corporation. Jim borrows money from the bank to build a new outbuilding and a new truck. Then he falls off his ladder and breaks his back. Jim doesn't have health insurance because he's in a high-risk occupation and the premiums are too high. He goes bankrupt from medical bills and lost income.
The difference between the MegaMaint CEO and Jim is that Jim is on the hook for everything. The bank and the hospital can go after everything Jim and his wife own in bankruptcy proceedings: their house, their bank account, their lake cabin, her jewelry, their stereo, their TV. They are forced to sell their house and property to pay off the bank loan and the medical bills.
The MegaMaint CEO is free to go out and do it all over again. Jim is out of his house, stuck in bed, broke, with a broken back.
How is that fair?
This is the key difference between a person and a corporation. No one is responsible in a corporation. As long as there's no proof of crime or entanglement with personal and corporate finances, no one is held accountable for a corporation's -- or the CEO's -- mistakes. To be fair, corporate bankruptcies are rarely this clear-cut. The CEOs are always giving themselves bonuses while the company's going bust, lying about financial prospects, or cutting deals with subsidiaries they secretly own. So CEOs are always involved with litigation after a bankruptcy.
Now the Supreme Court has also decided that corporations should be allowed to freely manipulate the electoral process via the media, by hiding behind "non-profit" slush funds that allow corporations to avoid responsibility for slanderous attack ads against their enemies. They can secretly donate millions of dollars to get candidates elected to office who have promised to do what these giant corporations want them to do: i.e., deregulate industries dominated by huge multinational corporations like Koch, BP, FOX News, Toyota, GlaxoSmithKline, etc., allowing them to escape even more responsibility for the things they do.
We have no idea who's giving to the political slush funds that finance these scurrilous ads. There are no reporting requirements. It could be foreign corporations or even foreign governments. Which would be a crime. But there's no way to find out because five guys on the Supreme Court think Target, Exxon, Burger King and Coca Cola are just regular folks.
For a more concrete example of corporate irresponsibility, consider the BP oil spill. Because it involves at least three corporations and dozens of engineers and rig workers, it will be impossible to find the person responsible for the spill in the Gulf. But BP has a history of serious safety lapses resulting in numerous explosions, deaths and spills from the Gulf, to Texas, to Alaska. Their safety record is abysmal, even compared to other oil producers.
Corporate management at BP is responsible for this climate of irresponsibility. People and animals have died, economies have been trashed and our land and seas have been despoiled. Undoubtedly a few lackeys will be fingered as the fall guys who caused the spill. But the ones truly responsible, the ones at the top who demanded that they get the oil out as fast as possible no matter what, will never be brought to justice. And that's the whole purpose of corporations: to dilute personal responsibility so that the guys at the top enjoy all the benefits and never face the consequences of their mistakes.
It's the Bizarro version of the old maxim: with great power comes no responsibility.