Of course it's not a fact, it's a philosophical idea (originally by Popper?). And of course it's controversial, especially in the US where 100% freedom of speech is protected by the constitution. But it's not that far fetched to think that the options are nearly free speech forever, versus completely free speech for a while.

It does hinge on the premise that speech is such a powerful tool that it can be used to remove fundamental freedoms. That's also just a hypothesis.