Let's talk about the implications of corporations having the same rights as people.
First, they should clearly have the same duties as people do.
- People have to sign up for the draft.
- People can go to jail and even be executed for their crimes.
- People get nationality at birth - which they can not easily change.
- People have to pay into social security and other taxes.
- People can marry
- People vote.
That last one makes it obvious - if we declared corporations get all the rights that people do, it would include the right to vote, which makes for obvious problems with rich people creating multiple corporations and getting extra votes. But that's not the end of it. Obviously, if you let corporations 'marry', then two gay men could make corporations and they could marry their corporations.
Some people like to 'translate' things and use that as an excuse. They say things like the people in the corporation have to sign up for the draft, can go to jail (or be executed), have nationality, pay into Social Security and other taxes, can marry and can vote, and that is good enough.
If that is true, by that same logic, the people in the corporations have free speech even if the corporation does not
To me, the biggest one is the possibility of jail. Corporations have their own goals and they can structure themselves to encourage the pursuit of those goals. Most of the time, that goal is to earn a profit. Usually the corporations structure themselves so as to pursue those goals legally. But not everyone is ethical. Sometimes people break the laws to get that profit. And sometimes the corporations structure themselves to encourage people to break the laws.
In those cases, the corporations need to be punished, not just the person that broke the law. If the crime that was committed was just theft, that's one thing. You can punish the corporation financially. If the crime resulted in a single death, that's a whole other story.
But lets talk about the single specific way the SCOTUS said corporations count as people: Free Speech. Not all speech is protected. There are types of speech that is illegal:
- Obscenity (usually applied to pornography)
- Fighting words "I had sex with your mother and you can't do anything about it."
- Imminent Threat (yelling fire in a crowded theater)
- Commercial speech has some restrictions. Trying to sell something means you give up certain rights - which is how the government can prevent cigarettes from advertising to children.
- National Security
- Public Employees. If you work for the government, the government can restrict what you say as a government employee. On your off time, you can say what you want.
- Corporations can punish employees or customers for saying things - that is, Free Speech protects you from the government, not your boss.
- For School discipline purposes.