Not only that, what makes you think corporate tax is paid only by shareholders rather than customers and employees?
A business needs capital to get started -- otherwise the founders wouldn't have to give ownership stakes to capitalists. But the capitalists also have the option to put their money in real estate or bonds or companies that sell to other countries etc. A company has to beat the after-tax ROI of those things in order to raise the money it needs -- so if the taxes go up, the ROI goes down, and they need to squeeze somebody else for the rest of the money, like customers and employees. Which, when it happens to every competing business in your country, they can do since no one can undercut them for the same reason they can't charge any less or pay employees any more and still raise capital -- everyone now has higher capital costs. The capitalists can move their money to an investment in another country more easily than the customers and employees can move around, so who eats the cost?
Ah ha, you say, but what about the companies that are no longer raising capital? Facebook is an established business. They don't need to raise any further capital, so their capital costs are irrelevant and we can tax those foolish capitalists who invested in them without expecting us to raise their taxes just as they were starting to see a return on their high risk investment. Which is true, except that you just convinced investors that it's not worth investing in a prospective competitor and have thereby entrenched Facebook's market position. Oops.