Every day for the past week, Kim Kwon-seop, 72, has joined thousands of others gathered near the home of South Korea’s impeached president, Yoon Suk Yeol. They were determined to shield Mr. Yoon from prosecutors who wanted to detain him on insurrection charges stemming from his short-lived declaration of martial law last month.
To them, it was the opposition who had committed insurrection, abusing its majority power at the Assembly to repeatedly block Mr. Yoon’s political initiatives. To them, the opposition’s parliamentary majority was invalid because the election last April was rigged. And to them, protecting Mr. Yoon was synonymous with protecting South Korea from “North Korea followers” who have taken root in every corner of their society, from the judiciary to schools to the news media.
South Koreans commonly dismiss such conspiracy theories as little more than online demagoguery spread by right-wing YouTubers with the help of social media algorithms. But amid the country’s entrenched political polarization, they have fueled the turmoil over Mr. Yoon’s situation, driving zealous believers like Mr. Kim to take to the streets in large numbers, calling for the president’s return to office.
“When I leave home for this rally every day, I tell my wife that this may be the last time she sees me alive, because I am ready to die for my cause,” Mr. Kim said. “This is not just about protecting President Yoon. It’s about saving my country for my descendants.”
If President-elect Donald J. Trump has a “Make America Great Again” movement behind him, Mr. Yoon has the “taegeukgi budae” (literally, “national-flag brigade”). It consists of mostly older, churchgoing South Koreans who enliven their rallies with patriotic songs, a wave of South Korean and American flags in support of their country’s alliance with Washington, and vitriolic attacks on the nation’s left-wing politicians, whom they fear would hand their country over to China and North Korea.
“We won!” flag-waving supporters of Mr. Yoon shouted on Friday when investigators retreated from the presidential residence after failing to serve a court warrant to detain him for questioning.
“Yoon Suk Yeol is depending on the South Korean version of MAGA to hold onto power,” said Ahn Byong-jin, a professor of political science at Kyung Hee University in Seoul.
Mr. Yoon invoked the right-wing fear and indignation when he declared martial law on Dec. 3 to “eliminate the despicable pro-North Korean and anti-state forces at one stroke.” But his attempt to place his country under military rule for the first time in 45 years lasted only hours. The opposition-dominant National Assembly voted to rescind it and later impeached him.
Suspended from office, Mr. Yoon now faces a trial at the Constitutional Court, which will decide whether to formally remove him. He is also subject to separate investigations from prosecutors, who have accused him of committing insurrection when he ordered troops to seize the Assembly and to detain his political enemies during his martial law.
With public surveys showing a majority of South Koreans wanting him ousted, Mr. Yoon’s strongest defenders are his flag-waving supporters and the right-wing YouTubers, who glorify him as a champion of promoting the alliance with Washington. These YouTubers, some with around a million subscribers, demand Mr. Yoon’s reinstatement and livestream pro-Yoon rallies, where speakers call the efforts to remove him a “coup d’état” at North Korea’s behest. They also reinforce political polarization by channeling conspiracy theories against Mr. Yoon’s progressive enemies.
Right-wing YouTubers have long boasted of their friendship with Mr. Yoon, after dozens of them were invited to his inauguration in 2022. In the wake of his botched martial law, Mr. Yoon left little doubt that he was a big fan.
“I am watching your struggle in real time through YouTube livestreaming,” Mr. Yoon said in a message to his supporters gathered outside his home on New Year’s Day. “Our country is in danger because of anti-state forces running amok, as well as forces in and outside who violate our sovereignty.”
During a rally on Wednesday, Seok Dong-hyeon, a lawyer who serves as Mr. Yoon’s spokesman, thanked right-wing YouTubers there and called the investigators trying to detain Mr. Yoon “a front” for the opposition.
“This is war,” he said. “And you are warriors.”
Like other democracies, South Korea has grappled with the role of social media in shaping politics. About 53 percent of South Koreans say they consume news on YouTube, higher than an average of 30 percent in 46 countries surveyed, according to a 2023 report by Korea Press Foundation.
Analysts worry that algorithm-fueled information bubbles, with people continually served more of the type of content they have expressed interest in by watching, are helping divide the nation. The language and conspiracy theories Mr. Yoon and his supporters adopted mirror those purveyed by right-wing YouTubers, said Hong Sung-guk, a former lawmaker and columnist.
“Yoon’s is likely the world’s first insurrection instigated by algorithm addictions,” Mr. Hong said.
A dozen participants in a recent pro-Yoon rally interviewed for this article were all firm believers in the conspiracy theories, saying that right-wing YouTubers were their primary or only source of news.
“They speak the truth,” said Kim Jae-seung, 72. “I no longer read newspapers or turn on TV. They are full of bias.”
Kim Yong-son, 70, pulled out his battered smartphone to show a video clip that depicted the progressive leaders as hellbent on undermining South Korea’s alliance with the United States and colluding with North Korea and China — viral content created by the popular right-wing pastor, the Rev. Jun Kwang-hoon.
In 1980, Chun Doo-hwan, the leader of the military junta that ruled the country at the time, justified imposing martial law by citing the threats from “North Korean puppets” and “dangerous elements” at home.
As his own political troubles deepened in the wake of scandals and disaster, Mr. Yoon aligned himself more openly with the radicalized political right. He accused unfriendly journalists of spreading “fake news” and called his political enemies subscribers to “Communist totalitarianism.” He even appointed a right-wing YouTuber as head of the center for training government officials.
Long before Mr. Yoon’s declaration of martial law, some of the right-wing YouTubers had urged him to take such an action to deal with his domestic enemies. They also spread sinophobia, hinting that China was a secret manipulator of domestic politics in South Korea, including its elections. Rallies of his supporters often ring with calls for “expelling Chinese.” Mr. Yoon raised fears of Chineses spies while defending his martial law.
Mr. Yoon and right-wing YouTubers also argue that election results in South Korea are no longer trustworthy. Pro-Yoon supporters often carry signs saying “Stop the Steal,” borrowing a term made popular by people in the United States who falsely claimed that the ballot count for the 2020 presidential election was manipulated against Mr. Trump. One of them, Shin Eun-ju, 52, said she believed the vote fraud theory, citing “YouTube” as her source.
The police and prosecutors, as well as the election authorities, have long dismissed the allegation as groundless. But when Mr. Yoon declared martial law, he also sent troops to the National Election Commission to investigate allegations of vote fraud. Military officers involved in his martial law decree had instructions, prosecutors said, to confiscate the commission’s computer servers and detain senior election monitors, tying, blindfolding and taking them to an underground military bunker for questioning about election fraud. (Martial law ended before any computers were seized or people taken away.)
Mr. Yoon and his lawyers have not commented on specific allegations, and they have broadly denied allegations of insurrection, calling his acts the legitimate exercise of presidential power.
“It’s clear that the president lost his mind to outlandish vote-fraud conspiracy theories while watching low-quality YouTube channels,” said Cho Gab-je, a prominent conservative journalist.
Mr. Yoon’s lawyer, Yoon Kab-keun, said the allegations of rigged elections were strong and divisive enough to merit an investigation.
Google Korea said it manages YouTube contents according to its community guidelines.
Ironically, it was also YouTube that helped news of Mr. Yoon’s declaration of martial law go viral on the night of Dec. 3, prompting citizens to rush to the National Assembly to delay the advance of troops and buy time for opposition lawmakers to vote down the martial law.
“It was a clash between the different roles of algorithms,” Mr. Hong said. “Algorithms help information go viral, but also help make you a slave to it.”
