Unrestricted freedom of thought and responsible freedom of expression are key factors in the process of intellectual and moral progression of humanity. These freedoms are intuitive and are attested to rationally. Any form of restriction to these freedoms inevitably results in tension since they stand in contradiction to the human existential condition of growth and self-realisation. Accordingly, the role of a successful religion is one of liberating humanity from factors restricting these freedoms and in addition to empower human beings to evaluate and critique established belief systems and status quo.
Islam challenged the existing norms and the belief systems of the time by appealing to human intuition and reason. This standard of critical examination was extended to its own teachings by verses that encouraged the initial community of Arabia to evaluate the content of the Quran. The appeal and success of Islam was squarely due to its being in tune with human intuition and reason. As such the religion Islam in this respect is subordinate to the existential facet of growth and therefore the debate of what level of freedoms Islam allows is a redundant debate.
The restrictions placed on the freedom of expression by the Sharia is no more than human intervention similar to the restriction applied by modern states in order to ensure state security and prevention of disorder among other things. Such restrictions are time bound and are open to revisions with the change of context; they are not immutable or eternal. Similarly, the lack of right to offend others in the process of critique is assured by human nobility primarily, and subsequently, echoed by Islam. In areas of freedom of thought and the level of freedom of expression religion merely reinforces what is already known intuitively and attested to rationally.
With this it is inconceivable that there should be an unquestionable sacred space within religion that restricts freedom of thought be it in the form of teachings contained within primary religious sources or their subsequent interpretations. More obviously there cannot be eternal law within Sharia that restricts the right of expression in the form of the laws of apostacy and blasphemy.