I have often critiqued the notion of free speech in my writing and defended the notion that some speech should be restricted and that, in certain contexts, some speech can be so damaging that, in theory, authorities should have the ability to bring criminal charges and convictions against offenders. The fact that we have such restrictions in classical Islamic law, I argue, is not only rationally and ethically defensible, but if we look at modern liberal secular states, we also see analogous restrictions on free speech. The only difference is that Islamic law deems certain ideas sacred while liberalism deems other ideas sacred and protects those ideas through all sorts of social and legal regulation. But of course, we are not conditioned to think in these terms which is why westerners continue to believe incorrectly (and naively) that their societies enjoy absolute freedom of speech while Islamic societies — i.e., societies following Islamic dictates such as the society of Muhammad ﷺ fourteen hundred years ago for example — languish under totalitarianism.
All that being said, there is still one aspect of “free speech” Muslims should embrace. The ability to criticize rulers should be protected. This is something liberal thought recognizes, at least in theory, and it is something Muslim historical precedent also supports. In different respects, the four righteous khulafa (caliphs) were criticized openly (and usually unjustly) and the khulafa did not react by having their critics silenced, imprisoned, or killed. If the righteous khulafa, who were the epitomes of just governance, could stand to be criticized, then how much more worthy of criticism are Muslim governments today?
It is a fact of human nature that those who are sincere, just, and honest do not care that they are criticized. In fact, they encourage feedback and appreciate being informed of wrongdoing and mistakes so that, if the criticism is valid, they can correct themselves and rectify matters. The wicked, however, despise criticism because they only are concerned with preserving themselves and protecting their interests. They have no concern for truth or justice, so they suppress criticism to the extent of their power.
In a well-known hadith, the Prophet ﷺ tells us that one of the main signs of hypocrisy is that when a person argues, he behaves impudently and quarrels in an insulting and evil way. The idea here too is that the hypocrite doesn’t care about the truth when he argues or debates. He cares about coming out on top no matter what the truth is. So, how much more is it a sign of hypocrisy that when a person or party raises complaints against a ruler, the ruler responds, not by investigation or a desire to address those complaints or an honest attempt to discover if those complaints are justified, etc., but instead the ruler responds with outright dismissal, crackdown, arrests, and even execution? What does that say about world governments today, especially in certain Muslim countries?
So yes, “free speech” is a significant part of Islamic ethics in this very particular sense and any rational person can see its importance. In all societies, whatever is considered sacred will be protected. The difference is, truly Islamic societies and governments — arguably none of which exist today — consider only God and His Message to be sacred and, thus, outlaw blatant blasphemy against God as that is attack on the very fabric of society and the very basis of justice and goodness. But all other regimes only consider their own power to be sacred and maybe a handful of other provincial notions as well, so they outlaw “blasphemy” against those while pretending to promote “free speech.”