The channel said the video had been sent in by a "fan (who) went to ask Chris Cuomo for a photo" and that he "legitimately thought his name was Fredo" because he only knew of him through radio host Rush Limbaugh who "repeatedly calls him" by that name.
"At this point Chris Cuomo loses it and threatens the man with violence," it said.
Fredo refers to John Cazale's character from The Godfather films, the weak and unintelligent older brother of Michael Corleone. Fellow radio host Mark Levin often refers to Cuomo as "the dumbest of the Cuomos".
"I thought that's who you were," the man says to Cuomo.
Cuomo responds, "No, punk-ass b**ches from the right call me Fredo. My name's Chris Cuomo, I'm an anchor on CNN. Fredo is from The Godfather, he was that weak brother. They use it as an Italian aspersion. Are you Italian? It's a f***ing insult to your people. It's like the N-word for us. Is that a cool f***ing thing?"
The man tells Cuomo he's a "much more reasonable person than you seem to be on television", prompting Cuomo to threaten him. "If you want to play then we'll f***ing play," he says. "If you've got something you want to say about what I do on television then f***ing say it."
He continues, "You're going to have a big f***ing problem. It's a little different on TV. Don't f***ing insult me like that. You called me Fredo, like I call you 'punk b**ch'. I'll f***ing ruin your s***. I'll f***ing throw you down these stairs like a f***ing punk."
The video, which ends with others getting in between the two to break up the altercation, went viral on Monday night. The term "Fredo" shot to the top of Twitter trends as debate raged over whether it was really a racial epithet on par with the N-word.
Trump campaign adviser Katrina Pierson wrote, "Did @ChrisCuomo just say that 'Fredo' is to Italians what the N-word is to black people? The N-word is a dehumanising word used against blacks who endured years of oppression. Fredo is a term from The Godfather, referring to the dumb brother. Equivocating the two is pure racism."
CNN spokesman Matt Dornic said the network was standing by its host. "Chris Cuomo defended himself when he was verbally attacked with the use of an ethnic slur in an orchestrated set up," he wrote. "We completely support him."
Internet users were quick to resurface clips of others, including Donald Trump Jr, being referred to as "Fredo" on CNN — even by a guest on Cuomo's own show.
"Does CNN's head of PR still think 'Fredo' is an ethnic slur after watching this?" Don Jr wrote. "Because if it's the N-word for Italians like @ChrisCuomo says, I don't understand why Chris seems so at ease with someone saying it here. An excuse just as fake as his news. #FredoCuomo".
Many defended Cuomo over the incident, which comes after a number of high-profile conservatives have been accosted and heckled in restaurants, including former White House spokeswoman Sarah Huckabee Sanders, Senator Ted Cruz, Department of Homeland Security secretary Kirstjen Nielsen and Fox News host Tucker Carlson.
"I say good for @ChrisCuomo," Fox News host Sean Hannity wrote. "He's out with his nine-year-old daughter, and his wife, and this guy is being a jackass in front of his family. IMHO Chris Cuomo has zero to apologise for. He deserves the apology."
