18th century America was influenced by the “Glorious Revolution” 0f 1688 in ‘mother’ England. And no one had a bigger impact on American attitudes towards freedom of speech than Englishmen John Trenchard and Thomas Gordon, who wrote about it in Cato’s Letter Number 15

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Freedom of speech is the great bulwark of liberty; they prosper and die together: And it is the terror of traitors and oppressors, and a barrier against them. It produces excellent writers, and encourages men of fine genius.

Tacitus tells us, that the Roman commonwealth bred great and numerous authors, who writ with equal boldness and eloquence: But when it was enslaved, those great wits were no more.

Postquam bellatum apud Actium atque omnem potestatem ad unum conferri pacis interfuit, magna illa ingenia cessere.
[After the battle at Actium ( when Octavian Caesar defeated Marc Antony) and when all power was brought to one peace (when Octavian was made Emperor Augustus), those great characters ceased.]

Tyranny had usurped the place of equality, which is the soul of liberty, and destroyed publick courage.

The minds of men, terrified by unjust power, degenerated into all the vileness and methods of servitude: Abject sycophancy and blind submission grew the only means of preferment, and indeed of safety; men durst not open their mouths, but to flatter.