If one line captured the essence of Saturday’s Boston Common rally and counter-protest, it was a quote halfway through Mark Arsenault’s Page 1 story in the Boston Globe:

“‘Excuse me,’ one man in the counter-protest innocently asked a Globe reporter. ‘Where are the white supremacists?’”

That was the day in a nutshell.

Participants in the “Boston Free Speech Rally” had been demonized as a troupe of neo-Nazis prepared to reprise the horror that had erupted in Charlottesville. They turned out to be a couple dozen courteous people linked by little more than a commitment to — surprise! — free speech.

The small group on the Parkman Bandstand threatened no one. One of the rally’s organizers, a 23-year-old libertarian named John Medlar, had insisted vigorously that its purpose was not to endorse white supremacy. “The rally I’m helping to organize is about promoting Free Speech as a COUNTER to political violence,” he had posted on Facebook. “There are NO WHITE SUPREMACISTS speaking at this rally.”

Indeed, nothing about the tiny rally, whose organizers had a permit, seemed in any way connected with bigotry or hatred. One of the speakers was Shiva Ayyadurai, an immigrant from India who is seeking the Republican nomination in next year’s US Senate race. As Ayyadurai spoke, his supporters held signs proclaiming “Black Lives Do Matter.”

But he and the others who gathered at the Parkman Bandstand had never stood a chance of competing with the rumor that neo-Nazis were coming to Boston. That toxic claim was irresponsibly fueled by Mayor Marty Walsh, who denounced the planned rally — “Boston does not want you here” — even though organizers were at pains to stress that they had no connection to Charlottesville’s racial agenda and intended to focus on the importance of free speech.

What happened on Saturday was both impressive and distressing.

A massive counter-protest, 40,000 strong, showed up to denounce a nonexistent cohort of racists. Boston deployed hundreds of police officers, who did an admirable job of maintaining order. Some of the counter-protesters screamed, cursed, or acted like thugs — at one point the Boston Police Department warned protesters “to refrain from throwing urine, bottles, and other harmful projectiles” — but most behaved appropriately. Though a few dozen punks were arrested, nobody was seriously hurt.

But free speech took a beating.

The speakers on the Common bandstand were kept from being heard. They were blocked off with a 225-foot buffer zone, and segregated beyond earshot. Police barred anyone from approaching to hear what the rally speakers had to say. Reporters were excluded, too.

Result: The free-speech rally took place in a virtual cone of silence. Its participants “spoke essentially to themselves for about 50 minutes,” the Globe reported. “If any of them said anything provocative, the massive crowd did not hear it.”

Even some of the rally’s own would-be attendees were kept from the bandstand. But when Police Commissioner Bill Evans was asked at a press conference Saturday afternoon whether it was right to treat them that way, he was unapologetic.

If a free-speech rally is held in a Boston Common pavilion but no one can get close enough to hear it, do the speakers make a sound?

“You know what,” he said, “if they didn’t get in, that’s a good thing, because their message isn’t what we want to hear.”

No, Commissioner Evans. It was not a “good thing” that people with a right to speak were effectively silenced by the operations of the police. The ralliers did nothing wrong. They followed the city’s rules. They did what police asked of them. They absorbed the slanders flung at them by the mayor and others. They didn’t try to shut their critics down, and they weren’t the ones hurling “urine, bottles, and other harmful projectiles.”

All they were guilty of was attempting to defend the importance of free speech. For that, they were unjustly smeared as Nazis and their own freedom of speech was mauled.

Boston was kept safe on Saturday, for which city authorities deserve great credit. But in the course of preventing a riot, those authorities rode roughshod over the free-speech rights of a small, disfavored minority. That is never a good thing, whatever the police commissioner may think.