If you can point out to me a corporation that is neither owned nor staffed by individuals, it'll help me to understand the objection.
What if a Corporation is owned by individuals who live in another country? Since the owners would not make purchases in the U.S. they would not pay any taxes at all. It also would be very difficult to monitor whether items purchased by Corporations were diverted to the personal use of the owners. Keeping track of the purchases of Corporations would require a Bureaucracy as large as the IRS. The only fair and practical way to implement a sales tax is have it apply to all purchases other than food, medical or a home.