You don't. That was the point of my post. Citizens United didn't grant corporations the rights of people and "corporate personhood" doesn't mean that anyway.
Nobody is talking about Citizens United (other than the people dragging it into the conversation just to point out that Citizens United is irrelevant).
Corporations already have the rights of people, because when corporations do crimes, the corporation, and not the people who constitute the corporation, is held legally responsible. What we are objecting to is that corporations are exempt from forms of punishment that are applied to natural persons. Either figure out how to make the punishment apply to corporations, remove that form of punishment from consideration for natural persons, or ignore the corporation for legal purposes and punish the humans behind the abstraction layer. It's pretty straightforward.