We can expand this topic by discarding our historical myopia and the tendency to live in the moment. Some Millennials may not see the light right away, although a sizable number of urban Millennials hold progressive views. So here's my theory.
The Founders came up in a period called "The Enlightenment", when the Church was losing its grip on defining how people should think about the practical world. Consider for a minute how Evangelicals and other Right-wing elements put God in the Constitution, when he's obviously "not there" -- it's a contract between citizens. They confuse the Constitution with the Declaration of Independence, which indeed invokes God, suggesting that the Rights of Man are God-given. People forget that the American colonists and generations who followed them were not the target audience of the Declaration's words. Instead, it was King George, in a time when people still spoke of a "Divine Right of Kings". You can see this obsequious language in the works of Locke or Hobbes (especially Hobbes) -- the grandfathers of the social sciences -- who primarily intended their words for the Sovereign. But in reality, the human race defined those rights and seized them as a quantum leap of human progress.
Similarly, the notion of personal property gets the same taint. It is the State which defines property rights, and the State can change them or take them away. Some safeguards in this respect are included in the Constitution.
There were no railroads at the Birth of the Republic, nor was there even so much as a telegraph. We had the postal service. So representative government was probably conceived with this in mind: they assumed that states and congressional districts would simply elect "wise men" who might "do the right thing". And beyond the invention of the telephone and radio, people communicated with their legislators using carefully worded letters posted in the mail. Perhaps some Power Elites could simply call their representatives or even their president to exert influence, but everything before Bill Gates and the internet still assured some degree of autonomy on behalf of legislators, and some degree of common sense filtering communications from the electorate.
The Founders also warned of factions, taken to mean political parties, extreme concentrated interests -- True Believers. They were never blind in this regard. But congressmen and senators were supposed to represent their districts or their states. Party was not their primary allegiance, at least not officially.
But today, there is this notion of winner-take-all in elections. Politicians worried about winning re-elections act less as leaders than as followers. They ignore the thoughts and interests of the losing opposition in their elections. They, like their partisan constituents, think of their election wins like sports enthusiasts view the NFL and Speed channel -- something akin to a religious allegiance and zero-sum game.
Others might expand or contend on this as they wish. But basically, I'm saying that free speech is fine, provided those who exercise it hold the Truth in prominence over everything. And I think that the Founders almost had a hard time imagining that a large number of people would not be Truth-Seekers, for after all -- the greatest of the Founders fit that description.
Instead, the free communication of the internet, cell-phone Tweets and similar channels has given way to more "white noise" of misinformation, disinformation, and the Murder of the Truth. Certainly, this is a paradox, given what Americans believe and hold to be important as a matter of their "fre-e-e-ee-doms".