No one said more rights; that they should have all the rights of a single citizen is contentious enough. What if, for example, we grant freedom of speech to this entity, and we take freedom of speech to include the funding of political parties, causes, or candidates? (That's how things are at present in the United States.)

No, that is not how things are. Companies do not have freedom of speech etc. in the USA.

Don’t they? In Burwell v. Hobby Lobby Stores, Inc., 573 U.S. 682 (2014) the Supreme Court did not address and answer whether for-profit corporations are protected by the free exercise of religion clause of the First Amendment of the U.S. Constitution, but the Court did recognize a for-profit corporation’s claim of religious belief (equal to the belief of its owners), sufficient for such a corporation to be exempt from a regulation that it (or its owners) religiously object to, if there is a less restrictive means of furthering the law’s interest, according to the provisions of the Religious Freedom Restoration Act of 1993.

The question of citizens untied, ect wasnt about if corporations get more or new rights, but if the people lose rights they had before if they are part of a group.

A person can hold up a sign, but can two people hold up a sign together.

Yeah, this is the critical legal reasoning behind Citizens United, and it doesn't get enough respect from people who dislike the practical outcome of that decision. You do not surrender your rights when you join an organization. Anything that one of its employees could legally do is something that the corporation (which is, as the saying goes about government, just another term for things we agree to do together) should be able to.

It's complicated and difficult to draw the lines and impossible to do it perfectly. But if Elon Musk wants to blow an entire fortune for the lulz, that's kind of up to him. And we shouldn't stop him.