A corporation can indeed be a person , or a few persons , or a large number of persons, and it must be so, there are no corporations of horses , of meerkats or jellyfish, rocks even trees.
There is incorporation of imaginary persons , but these are necessarily imaginary corporations. A real corporation requires real persons to exist.
Incorporating is a means of shielding persons from certain kinds of loss and indemnification , but you state and I agree that being incorporated does not protect the persons of the corporation from enforcement of laws such as murder , so that if IBM kills there will be persons from IBM put on trial , not anything intangible .
So why should the Supreme court find that those who join corporations should loose the rights due them as persons or citizens?