The idea that all corporate money eventually winds up being spent by a tax-paying consumer somewhere breaks down under these circumstances:
- The corporation just sits on the cash
- The corporation sends the money overseas to a tax haven somewhere
- The corporation outsources jobs.
It seems fair - if a corporation wants to have free speech like a person, have rights like a person, and own assets like a person, it should pay taxes like a person. Otherwise, people would be forming communal corporations ("financial guilds", if you will), and running all of their income through them in order to reduce their tax rate to zero.