Washington (CNN) Vermont Sen. Bernie Sanders on Monday stood by his partial defense of Fidel Castro's Cuban revolution, stating bluntly: "The truth is the truth."

The senator from Vermont has faced a wave of bipartisan criticism since his interview on CBS' "60 Minutes" aired Sunday night in which he praised a "literacy program" the Cuban government launched in its first years and asserted that "it's unfair to simply say everything is bad" with the way Castro ruled the country.

Speaking during CNN's presidential town hall in South Carolina Monday night, Sanders again talked up the "literacy program" Cuba launched in its first years.

"There were a lot of folks in Cuba at that point who were illiterate. He formed the literacy brigade," Sanders said. "(Castro) went out and they helped people learn to read and write. You know what, I think teaching people to read and write is a good thing."

He added: "I have been extremely consistent and critical of all authoritarian regimes all over the world including Cuba, including Nicaragua, including Saudi Arabia, including China, including Russia. I happen to believe in democracy, not authoritarianism."

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