The Libertarian presidential candidate's interview with Guardian reporter Paul Lewis came on the heels of an exchange with HBO, which was apparently just as heated.
"I could hear some loud voices just then," Lewis joked. "Is is the same questions? You get the same questions again and again and again?
"I'm an idiot," Johnson responded. "Really. I'm the dumbest guy that you've ever met in your whole life."
"I'm trying to work out if that's sarcasm or not," Lewis replied.
"It is," Johnson said. "I hope it's sarcasm."
He went on to reference his high-profile gaffe on MSNBC's "Morning Joe" in September, when he responded to a question about the Syrian civil war by asking: “And what is Aleppo?”
"I'm not a dummy," Johnson went on. "I'm not."
The interview devolved further when Lewis questioned Johnson about why he lags in fourth place in a race where both major-party candidates are unpopular.
"Why are you even interviewing me? I don't get it," Johnson fired back. "If I'm doing so poorly, is this to preside over a funeral here? It's not a funeral, it's a celebration."
When pressed on his tax policy, which Johnson has said involves abolishing income tax and corporation tax, the Libertarian candidate segued into a bizarre metaphor about the legalization of marijuana.
"Look, I came out for the legalization of marijuana. Let me just use that as an example," Johnson barked. "And I will tell you that I had people in my face for years and years and years talking about how stupid and how idiotic it was that we should allow marijuana to be legal."
"But what's that got to do with your tax policy?" Lewis asked.
"It's leadership," Johnson said. "It is leadership."