Members of a group that identifies itself as a coalition of progressive university students broke into the residence of US Ambassador Harry Harris in Seoul on Friday. They climbed over the wall using ladders and staged a protest against the US presence in South Korea.

A photo the group posted on its Facebook account shows the activists unfurling banners accusing the US of demanding a 500 percent hike in costs to South Korea for the upkeep of its troops here. A large banner read, “Leave this soil, Harris.” The protesters reportedly shouted, “Leave Korea, America,” and “Withdraw US forces” as the police took them away.

About five minutes before climbing over the wall, 19 members of the group had staged a protest in front of the residence, displaying placards and shouting slogans. They also had two ladders.

But the three police officers present -- two on patrol and one in a sentry post -- did not attempt to disband them immediately. Two male protesters held back the two patrolling officers while the other protesters began climbing the ladders.

Dozens more police officers arrived and entered the residence after getting permission from the US Embassy. They arrested all six male protesters, but did not arrest the 11 female protesters. Instead they surrounded the women, waiting for policewomen to come and arrest them.

A police officer reportedly said it was important to take out the female protesters “safely” rather than quickly “because (male) police officers may get in trouble later if they had physical contact with them.”

Should a policeman wait for a policewoman to come and catch a criminal who is a woman? This is absurd. How can law and order be maintained this way?

President Moon Jae-in’s administration has a lot to answer for this passive police response. A police reform panel set guidelines directing the police to refrain from using physical force when cracking down on illegal protests. This guidance needs to be revised to ensure the immediate arrest of violent protesters.

The group claims to advocate progressivism, but it actually has defended North Korea and sometimes taken the side of the ruling camp.

Early this month its members illegally climbed ladders to the base of the statue of King Sejong in Gwanghwamun Square in downtown Seoul to stage an anti-US protest.

Last year it took the lead in creating a “committee to praise North Korean leader Kim Jong-un and welcome his visit to Seoul.” Moon had invited Kim to South Korea in return for his visit to Pyongyang, but he has not visited the South yet. The group publicized Kim and his possible visit throughout Seoul.

On Monday in the square, activists affiliated with the group called for the disbandment of the main opposition Liberty Korea Party and the imprisonment of its leader, Hwang Kyo-ahn, as well as the ouster of Prosecutor General Yoon Seok-yeol. In April, its members occupied Liberty Korea Party Floor Leader Na Kyung-won’s office at the National Assembly, demanding that both Hwang and Na resign.

With anti-Japanese sentiment rising over Tokyo’s decision in July to restrict exports to South Korea, it has condemned the opposition party for “collaborating with Japanese raiders.” Since a corruption scandal hit former Justice Minister Cho Kuk, the group has demanded reforms of the prosecution investigating his family.

Although the group may be small and is probably disregarded by most university students, considering the shaky US-South Korea alliance its behavior is not a thing to be trifled with.

Cracks in the alliance surfaced after the Moon administration decided to terminate a deal to share military intelligence with Japan despite Washington’s opposition. The US kept a neutral position on the issue of sovereignty over the Dokdo islets, also claimed by Japan, but criticized South Korea’s latest military drill near the islets. The US-South Korea joint military exercises have been greatly scaled down or discontinued.

South Korea is currently beset with troubles at home and abroad. It is experiencing economic difficulties and public confidence in the Moon administration is falling after the Cho scandal. The US alliance, the axis of Korea’s security, is weakening. Pyongyang has stepped up its threats since its talks with the US broke down.

If anti-Americanism flares up in this situation, it will put both the security of South Korea and its economy at greater risk. Crooked actions by the pro-North Korean leftist group must not be tolerated anymore. The government should already have clamped down on it, before it came to this.

The group is small but violent and persistent. Its intrusion into the US envoy’s residence is a serious matter. The trespassers must be punished strictly. Enough is enough. Now is the time to draw the line. The government ought to prevent anti-Americanism from spreading.