Without a corporate income tax owners can withdraw the incomes minus dividend taxes. With corporate income tax they can withdraw income minus corporate income tax minus dividend taxes. How can you say they're not the ones paying the tax when the money could go directly in their pockets if not for the tax?
Corporate money belongs to the corporation, not to the shareholders. Corporation is a separate legal entity, it has its own property rights and its own will power. It also has an obligation to heed the interest of all stakeholders, including shareholders, employees, managers, customers, the public etc. Shareholders exert certain level of control over corporation, similar to how the board, the management, the employees and the customers have their own power, and while shareholders can change the board, they don't have any kind of fine-grained control, and even their control over the board might be limited by the corporate charter.
To say that corporate money belongs to the shareholdes is to trivialize a very intricate balance of powers.
Corporate income tax is a tax on corporate income. You can't call it shareholder tax any more than you can call it employee tax (or employment reduction incentive, if you will), or manager bonus tax, or capital re-investment tax. It's all of the above, and then some. It's not just one of the above.
My understanding is that most tax incidence economists believe the corporate income tax is primarily born by shareholders. Sure it's a very complicated issue, but if you pin it on one party then shareholders is the least inaccurate.
Well, no.