There is no such thing as a "natural right of freedom of speech". If one sovereign in the history of mankind decides to allow unrestricted freedom of speech in its constitution, it is just that: an episode in the history of legal systems established by humans. It can turn out as a bad idea, or a milestone for better societies. We will see. In no way is it a "natural right". Not even would it be a natural right, if it was mentioned in the bible as one of the 10 commandments from god (disregarding the FACT, that there are some serious restrictions of freedom of speech in that: "Thou shalt not bear false witness against thy neighbour").
In fact, there is no such thing as a natural right at all. Rights are derived from value systems, and the choice of value system is mostly based on aesthetics. There is no way to say whether the Western Christianity-based value system is "better" than, say, the Confucian value system, because the word "better" cannot be defined from first principles (without invoking a particular value system).
