By Edward Achorn

President Trump is crude and obnoxious, especially on the Twitter platform. Like many politicians, he says many things that are patently untrue. His propensity for bullying and insulting others disgusts many decent Americans.

But his enemies have turned off people, too.

Their actions have caused Mr. Trump’s base to rally around him, arguably strengthening him politically rather than weakening him. I have often thought Democrats would have been much better off just letting him hang himself.

Now these adversaries are seeking to blunt one of his political weapons, his Twitter account, which has 80.4 million followers.

Pressured by anti-Trump media operations seeking to ban his tweets, Twitter this week began “fact-checking” the president’s opinions.

Twitter started off by carrying the flag for mail ballots, one of this year’s big causes for those on the left.  President Trump declared that the use of mail ballots — which breaks the chain of custody between the dispensation of ballots, the voter and the ballot box, and is thus obviously susceptible to fraud — would be “substantially fraudulent.”

Twitter umpires added this to the tweet: “Fact-checkers say there is no evidence that mail-in ballots are linked to voter fraud.”

That opened an industrial-sized can of worms.

Is Twitter now going to police the speech of everyone? Or just people or parties whom the technology platform doesn’t like?

Is “fact-checking” a first step toward outright censorship of tweets that Twitter deems inaccurate?

Who are the umpires deciding what is truth? The White House quickly painted a target on Yoel Roth, Twitter’s “Head of Site Integrity,” who in the past has referred to Trump and his team on Twitter as “ACTUAL NAZIS” and labeled Mr. Trump a “racist tangerine.” Mr. Roth also tweeted in 2016: “I’ve never donated to a presidential campaign before, but I just gave $100 to Hillary for America. We can’t [f-word] around anymore.”

Twitter fired back, saying Mr. Roth was not involved in its fact-checking operation. But the uproar certainly raised the question: What about the biases of Twitter employees? Who has been given the philosophically impossible task of determining with absolute precision what is truth and what is not? Is Twitter not merely substituting its own opinions for the president’s?

Is Twitter now liable for everything posted on its site? Has it become a publisher, favoring one side of the political spectrum rather than a kind of public utility permitting speech for everyone? Does that mean it could be sued into oblivion?

It is unclear where this is going.

My own hope is that such social media platforms will permit a maximum of free speech and stay out of political debates.

There are people all over Twitter who could provide “fact-checking” of Mr. Trump without the site’s putting its massive thumb on the scale. Banning or constraining speech to “protect” the public from falsehoods and promote “safety” is the classic path of totalitarians.

The strength of America is that people, for centuries, have been able to engage in freewheeling discussions, advancing ideas that — while deeply wrongheaded and permeated with falsehoods in the eyes of people on the other side — do move society toward justice. In the nineteenth century, for example, many wished to ban public debate about the explosive issue of slavery. But the debate went on.

The news media and the American Civil Liberties Union used to defend free speech fiercely. Sadly, the ACLU has dropped the ball and many left-leaning news organizations are increasingly on the side of stifling speech they do not like.

The greatest American, our first president, George Washington, warned: “If freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter.”

More than 150 years later, Democratic president Harry Truman issued a similar caution. “Once a government is committed to the principle of silencing the voice of opposition,” he said, “it has only one way to go, and that is down the path of increasingly repressive measures, until it becomes a source of terror to all its citizens and creates a country where everyone lives in fear.”

In my years as a journalist advocating First Amendment rights, I often turned to the wisdom of John Milton’s 1644 speech “Areopagitica”:

“Give me the liberty to know, to utter, and to argue freely according to conscience, above all liberties,” Milton said.

“Let [Truth] and Falsehood grapple; who ever knew Truth put to the worse in a free and open encounter?”

Let political speech — however wrongheaded — flourish on social media. That is the best (and really only) protection of the people, as centuries of experience have demonstrated.

(Read Edward Achorn’s books about American history.)