It's just ridiculous that anybody would buy this stuff," Munger, 99, told CNBC's Becky Quick during a livestream of the event, adding: "It's totally absolutely crazy, stupid gambling."
"I think the people who oppose my position are idiots, so I don't think there is a rational argument against my position," he said.
Munger's comments come amid an avalanche of problems for crypto investors over the past year.
He's previously urged the U.S. government to ban cryptocurrencies, and may partially get his wish as the crypto industry faces rising regulatory crackdowns.
"In other words, an adviser may custody crypto assets at a bank, but banks are cautioned by their regulators not to custody crypto assets," Uyeda wrote.