"It's absolutely inconceivable that any American as old as him, knowing everything we know about Fidel Castro and the people that he's murdered over the years, that anybody could support him in any way," one man said.
One woman told Jones she likes Sanders, but admitted "I don't like" his praise of the Cuban dictator.
Jones asked other South Carolinians about Sanders' many plans for radical reform and how they would be paid for.
"Is there any chance that Bernie can pay for all of these?" Jones asked a supporter.
"Absolutely not. Absolutely not," one man responded. "I tried to make payroll every single week. I can't make payroll half the time."
Another supporter told Jones she expects a tax increase to pay for the plans.
"If you look at Europe and what they pay, like 60 percent of their taxes go towards that," she said. "That's how he's going to pay for it, by taxation."
Sanders was heavily criticized for his proposals Tuesday night during the Democratic presidential debate.
"The math does not add up," Sen. Amy Klobuchar told Sanders. "In fact, just on '60 Minutes' this weekend, he said he wasn't gonna rattle through the 'nickels and dimes.' Well, let me tell you how many nickels and dimes we're talking about.
"Nearly $60 trillion," Klobuchar added. "Do you know how much that is, for all of his programs? That's three times the American economy. Not the federal government. The entire economy."