WATCH: David Corn eviscerates 'dimwit' Devin Nunes for his 'bizarre' handling of Trump investigation

A Saturday morning AM Joy panel on House Intelligence Committee head Devin Nunes (R-CA) turned into a group attack on the lawmaker's credibility as well as his mental capacity to investigate the Trump White House after his disastrous week.

Speaking with MSNBChost Joy Reid, Mother Jones editor David Corn explained that he was stunned earlier in the week when Nunes told him he was unfamiliar with Trump confidantes Roger Stone and Carter Page -- both of whom are under investigation.

"You know, every once in a while you end up as a reporter, you ask a question, you get an answer and you're flabbergasted," a laughing Corn explained. "I was stunned. There was no logical explanation."

Corn then made a stab at explaining.

"Either he's a dimwit who hasn't read a single story about the matter he's supposed to be vetting or he has some brain disease and can't remember or he was lying to me," Corn remarked. "Those are the only options I can think of. It was a bizarre moment and you're right, we could spend the next hour talking about all the weird things and bizarre things he did this week from cancelling hearings to coming forward with incomplete information to rushing to Trump."

"It is a breakdown, and I say this to be serious," he continued. "It's the breakdown of the Congressional intelligence oversight process and the only reason we let the Executive Branch do secret work in terms of espionage, counterintelligence, counter-terrorism is because they've overseen by the Legislative Branch. And Devin Nunes just showed this week that there is a complete breakdown in that process."

Watch the video below via MSNBC: