This is John Stuart Mill discussing freedom of speech as an economic issue in his Principles of Political Economy (1848), in my view the best single text on economics ever written. Freedom of speech, as he writes in the passage below, is a crucial element in allowing minds to wander where they will and consider all kinds of ideas and alternatives, and then to debate freely each and every one of the various considerations that different individuals might have. Without such freedom of thought, an economy cannot prosper. What is specially interesting are the examples from his time where different ideas have been suppressed. It would almost entirely be the reverse opinions that might be suppressed today.
The notion, for example, that a government should choose opinions for the people, and should not suffer any doctrines in politics, morals, law, or religion, but such as it approves, to be printed or publicly professed, may be said to be altogether abandoned as a general thesis. It is now well understood that a régime of this sort is fatal to all prosperity, even of an economical kind: that the human mind when prevented either by fear of the law or by fear of opinion from exercising its faculties freely on the most important subjects, acquires a general torpidity and imbecility, by which, when they reach a certain point, it is disqualified from making any considerable advances even in the common affairs of life, and which, when greater still, make it gradually lose even its previous attainments….
Yet although these truths are very widely recognized, and freedom both of opinion and of discussion is admitted as an axiom in all free countries, this apparent liberality and tolerance has acquired so little of the authority of a principle, that it is always ready to give way to the dread or horror inspired by some particular sort of opinions. Within the last fifteen or twenty years, several individuals have suffered imprisonment, for the public profession, sometimes in a very temperate manner, of disbelief in religion; and it is probable that both the public and the government, at the first panic which arises on the subject of Chartism or Communism, will fly to similar means for checking the propagation of democratic or anti-property doctrines. In this country, however, the effective restraints on mental freedom proceed much less from the law or the government, than from the intolerant temper of the national mind; arising no longer from even as respectable a source as bigotry or fanaticism, but rather from the general habit, both in opinion and conduct, of making adherence to custom the rule of life, and enforcing it, by social penalties, against all persons who, without a party to back them, assert their individual independence. (Mill ( 1921): 940)
Did you make it this far? Not everyone finds Mill all that easy to read, but once you get the rhythm there is no one like him anywhere.