Freedom of expression, as defined in the US, sure. But not everybody in the internet shares the definition.

E.g. as a European my idea of freedom of speech is not limited to the things I am allowed to say, but also about whether spaces exist in which I can say them. US style freedom of speech, doesn't produce any more insightful or free discourse than over here. In fact I'd argue it produces a discourse where voices win that are the loudest, most outrageous and least respectful, while voices that are more reasonable are frightened away.

It is the same thing that happens if a state gives up her monopoly of violence: The strongest dominate, while the weaker, more peaceful ones suffer.

Freedom is not just the freedom to do X, it is also the freedom of not having X done to you, as well as the freedom of living in a space where doing X is actually possible.

This means a free society does not have to endure all voices, especially those that aim at harming others or have the goal of using freedom of speech to get rid of the free society. Don't like the rules of a free society? Then you don't get to easily claim the protections granted by one. You can't whine to the referee if your goal is to get rid of the referee — I mean you could, but that would be pathetic.