This is horribly incorrect. Freedom of Speech is a larger concept outside of how it is (and can even possibly be) codified in law. The US Bill of Rights is phrased in terms of a restriction on the government, because that's the only line that can be straightforwardly drawn within the framework of the Constitution.

An example of the concept being applied to quasi-public entities, with enough generality for the legal realm: https://en.wikipedia.org/wiki/Pruneyard_Shopping_Center_v._R...