After Joe Biden called Antifa an "idea, not an organization" at the first presidential debate, Dave Rubin shared his firsthand experience with the far-left group's violent protests at his events on "Fox & Friends."

"An idea doesn’t burn down buildings. An idea doesn’t throw Molotov cocktails at people. An idea doesn’t assault people on the street. People do that," the host of "The Rubin Report" said.

"If what Joe Biden is trying to say is that they don’t have laminated business cards ready to hand out when they are doing these things, then I suppose he’s correct, but I’ve done many public-speaking events, usually about free speech and free markets, capitalism, good stuff, no bigotry, no racism or hatred involved and Antifa has shown up and violently protested, pulled fire alarms," Rubin explained.

The "Don't Burn This Book: Thinking for Yourself in the Age of Unreason" author pointed to a video on Twitter showing an elderly woman trying to cross the street to get to one of his events in Canada as protesters are blocking it and calling her a Nazi.

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"These are bad people and by design they are decentralized, so when Biden is saying they are an idea, it's because he’s afraid that so much of his base, his radical base is actually in line with Antifa and if he says something about them, they will end up coming for him."

His comments come as President Trump, after condemning White supremacists on the White House south lawn to reporters Wednesday, called on his Democratic rival to condemn Antifa after an exchange between the two during Tuesday night's debate.

"Antifa is a real problem, because the problem is on the left and Biden refuses to talk about it. He refuses to issue the words 'law and order' ... he can’t say the words because he’ll lose the rest of the left. So he’s got to condemn Antifa. Antifa is a very bad group," Trump said.

The president last week introduced a plan that would designate Antifa a terrorist organization, something he had suggested doing in the past.

Andy Ngo, a Portland-based journalist, is seen covered in unknown substance after unidentified Rose City Antifa members attacked him on June 29, 2019 in Portland, Oregon. (Photo by Moriah Ratner/Getty Images)

Andy Ngo, a Portland-based journalist, is seen covered in unknown substance after unidentified Rose City Antifa members attacked him on June 29, 2019 in Portland, Oregon. (Photo by Moriah Ratner/Getty Images)

Antifa has been behind violence and riots for years, with the group tracing its roots back to Portland, Ore., in 2007, but has been behind a surge in violence in cities across the country during the summer in places like Portland, where the federal courthouse was besieged by left-wing radicals for months.

Attorney General William Barr recently said: “I’ve talked to every police chief in every city where there has been major violence and they all have identified Antifa as the ramrod for the violence."

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Meanwhile, Andy Ngo, a journalist who has covered Antifa for years and was severely injured in an attack by Antifa rioters last year, pushed back on the claim that the group is merely an “idea.”

“If Biden made the comment last year, I think it would be excusable,” Ngo, who is also the author of an upcoming book on the group, told Fox News. “But by now, we've had months and months of rioting where there are clear Antifa-organized elements. We've had hearings in Congress related to Antifa. There is evidence in the criminal complaints against some charged showing Antifa ties.”

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Ngo continued, “Biden's statement shows that on this subject, he – and the Democrats – want to keep the liberal status quo, which is to downplay and deny the threat of the organized militant far-left.”

Fox News' Adam Shaw contributed to this report.