I know that's part of the Supreme Council's current justification for why corpos deserve natural rights, but I don't really see what it actually has to do with anything. Regardless of how corpos might be regulated, the individuals associated with a corpo are all still capable of exercising their free speech rights in their own individual capacity. Declaring that the government-created legal entity should not be able to direct individuals to speak a certain way fundamentally preserves those individuals' rights. The corpo's owners are also still able to freely speak on the corpo's interests using their own individual rights.
