This is the problem with freedom of speech in general. Freedom of speech is a good thing on paper but because humans rule on the basis of morals in practice freedom of speech is a very murky place. Allow me to present you with a scenario:

John believes that the Nazi party was correct in its views and policies and feels that the Allied forces conspired against the Nazi party and created this "false" genocide in order to ensure that Europe never encounters a situation like this again. It is john's right to believe this as we as humans hold freedom of speech as one of our core values. John was arrested yesterday and extradited to Germany for holocaust denial.

Is john's freedom of speech not being denied? The popular consensus says that the holocaust happened. Does that mean John is not allowed to question it? A very murky place indeed.