My argument is that only people are people. Corporations are explicitly different, and there's no good reason for corporations to automatically have the same rights as people.
The whole problem with Citizens United is that it uses the 1st amendment right of free speech for people to grant corporations the right to make political donations, which makes no sense. Corporations are not people and donations are not speech. It's no wonder that this leads to a political system that represents corporations more than it represents people.