Yoon Suk-yeol, the presidential candidate of the main opposition People Power Party, remarked in a recent interview with a local news organization that if he takes power, his administration should investigate corruption allegations involving his predecessor‘s regime.

Asked whether his administration would seek to eliminate the evils of the previous administration as President Moon Jae-in’s government did, he said “it should.”

Regarding the possibility of criticisms that investigations into the previous government will become political retaliation, Yoon said that the president will not get involved in investigations, and that all of the investigations will be conducted in accordance with set procedures.

The ruling Democratic Party of Korea said that Yoon effectively vowed to take revenge on the Moon government under the pretext of “removing evils“ if he comes to power.

A senior official at Cheong Wa Dae, the South Korean presidential office, said he was displeased with Yoon’s remarks that the Moon regime committed many crimes using prosecutors.

What Yoon said is not wrong. If the ruling party and Cheong Wa Dae did nothing suspicious, they would have no reason to be displeased.

Youn Kun-young, a Democratic Party of Korea lawmaker who served Moon as director of the situation room at Cheong Wa Dae, argued that the current regime did nothing that could raise suspicions. But the argument sounds less than convincing.

The president was mentioned many times in a written indictment of 13 suspects, including his Cheong Wa Dae secretaries and a senior police officer on charges of intervening systematically in the 2018 Ulsan mayoral election to get Moon’s old friend elected. This case is on trial.

After Moon asked his aides when the government will decide to shut down the operation of the Wolsong-1 nuclear reactor, the Ministry of Trade, Industry & Energy and state energy firms intentionally distorted its economic viability data in consultation with Cheong Wa Dae and indefinitely suspended the refurbished reactor, causing a huge loss.

Special favor allegations involving Rep. Lee Sang-jik and Moon’s son-in-law, who was employed in a Thai budget air carrier that Lee is suspected of owning, are under investigation.

In an apparent move to follow Moon’s instruction to reinvestigate a bribery case involving a former vice justice minister -- though charges were already dropped -- a prosecutor in collaboration with a presidential secretary illegally banned the former vice minister from going abroad. The prosecutor and the former Cheong Wa Dae secretary now stand on trial. The former vice justice minister was acquitted.

Quite a few suspicions that infuriated people were raised under the Moon regime, but most were not investigated properly. Pro-government prosecutors appointed to major posts under the pretext of reform dawdled or obstructed investigations unfavorable to the government. The Supreme Court chief justice appointed by Moon filled important posts with judges supportive of the president.

It is indisputable that corruption allegations must be investigated, and those found responsible punished. This can hardly be called retaliation. The Moon regime is not sacrosanct and inviolable. It is a double standard to argue what they did was a righteous fight against evil while dismissing the same things that others do as revenge.

But there is one thing to be wary of. The boundary between an anticorruption drive and political retaliation is fuzzy. Investigations must not go to extremes. Elimination of past evils was a slogan of the Moon regime to launch investigations targeting the two previous conservative governments. In the course of investigation, five people committed suicide. On the surface, the Moon government justified the drive as a struggle to remove irregularities. But in fact, it was close to political revenge. Investigations must be thorough, but proper and impartial. Above all, they must serve the restoration of the rule of law.