That's all very well and good but aren't you arguing in a circle? You're essentially saying "since shareholders have absolute power over an enterprise, therefore they have absolute power over the enterprise". Sure, but we're arguing that it's not a good idea to have companies be immune to any public accountability or and democratic control. In fact we already do this: there are myriad laws that constrain the behaviour of companies: rules about financing, transparency, pollution, taxes, etc.
I read the comment as being a complaint specifically about the rule that board members should have to act in the financial interest of shareholders. If the intention was to criticize ownership rights of shareholders or to argue for legal limitations on the powers of a company's owners, then my response definitely doesn't address that.