• Owning people, otherwise known as slavery, is currently illegal in the United States as per the 13th amendment, as well as in most other countries of the world.
• Corporations have been ruled by the courts, at least in the US, to be legally persons, having thus all rights as human beings under the constitution and the law, such as the right to free speech.
• To own stock in a corporation is to own a part of that corporation.

Thus, because owning stock in a corporation is to own a part of that corporation and corporations are people, owning stock is owning people. Owning people is slavery. Slavery is illegal. Owning stock in corporations is illegal slavery.