> most economists (left and right) believe the optimal corporate tax rate is 0%

Please provide some evidence, because I think only a narrow group of right-wing economists say that.

Taxes are generally applied where money is transacted, such as income and sales. For economic and legal purposes, corporations are entities just like people. They earn money, save it, pay it, invest it, etc. IME, they try to come up with every argument, sane or bizarre, to avoid contributing their share of taxes.