The prosecutorial investigation into “evils” is apparently set to target former President Lee Myung-bak.

His former Defense Minister Kim Kwan-jin was arrested Saturday on charges of involvement in the Cyber Command’s illegal political activities, in which personnel left comments critical of the opposition.

His former director of the National Intelligence Service, Won Sei-hoon, is serving a four-year prison term for running an unlawful cyber team of civilians and NIS retirees to meddle in elections.

Kim was reportedly briefed on the command’s covert operations and reported them to Cheong Wa Dae. He is said to have told prosecutors that Lee ordered him to hire personnel for the command who are “on our side.”

In light of technical procedures, the next step for the prosecution is interrogating Lee himself.

If the prosecution has secured sufficient evidence, it must not dither. Lee, if summoned, must reveal the truth with a buck-stops-here attitude and bear the blame if there is anything he should take responsibility for.

The personnel of the command leaving comments to criticize the opposition is worthy of criticism. But it is no time to throw out the baby with the bathwater. The command was established in 2010 to counter North Korea’s escalating cyberterrorism, including internet comments bashing the then conservative South Korean government. The North attempted distributed denial-of-service attacks on South Korean government agencies, financial institutions and news media. The people wanted the government to strengthen its cyberwarfare capabilities.

Lee said to reporters Sunday, shortly before flying to Bahrain, “For about six months, I have watched the current government try to clean up deep-rooted evils. Now I wonder whether this is reform, an act of venting its anger or political retaliation.”

The ruling Democratic Party of Korea denounced Lee as the “originator of evils” and called for the prosecution to interrogate him. It is commonly thought that both Cheong Wa Dae and the party want to dig up dirt on the Lee administration and punish those involved. Even if Lee is cleared of suspicion of having illegally been involved in the cyber political campaign, he will find it difficult to avoid an investigation into other suspicions.

In a radio talk show on Monday, Song Young-gil, a Democratic Party lawmaker, fumed at Lee’s mention of political retaliation.

“Who humiliated and drove to death former President Roh Moo-hyun, who was living out of town?” he asked.

Song seemed to conclude that Lee retaliated against Roh politically. His words give an impression that someone must avenge Roh’s death on Lee.

On the Cheong Wa Dae website, people have posted petitions calling for Lee to be barred from leaving the country. They amount to prejudging the former president as guilty and smack of a kangaroo court.

If allegations are investigated on such inexcusable charges as bribery, the probes should be all the more rigorous when it comes to former presidents. However, if a former president is indicted for a government agency’s deviation from its mission of leaving comments in response to the North’s cyberterrorism, the current government’s drive to “eliminate evils” will likely be seen as off-target and emotionally motivated. About 1.15 percent of all comments left by the command have been judged by a court as problematic.

The investigation into a past regime seized by a political opponent can hardly avoid giving the impression of retaliation, no matter how it is put forward as an effort to restore justice. Exempting ideologically similar administrations of the past from investigation makes it harder to dispute such criticism.

When the regime changes, the tables turn. What is worrisome is the nation may enter a vicious circle based on “the elimination of evils.”

If a former president should be interrogated just because there were illegal deviations under a ministry, no president will be free of investigation after leaving office.

It is feared that the spiral of cleaning up evils will drag down national politics.