U.S. Ambassador Mark Lippert was discharged from the hospital Tuesday, much to the relief of the Korean people who have been expressing support and sympathy for the envoy, who was attacked by a knife-wielding assailant on March 5.

Much to the chagrin of the public, however, political parties are attempting to exploit the incident for their own political gain ahead of next month’s by-elections. The ruling Saenuri Party and the main opposition New Politics Alliance for Democracy were united in condemning the attack by Kim Ki-jong, a minor NGO leader. During separate visits with Lippert on Sunday, leaders of the Saenuri Party and the NPAD stressed the importance of the Korea-U.S. alliance, cautious that the incident might damage Seoul’s relations with Washington.

However, very soon the two political parties were back to their usual ideological battles, verbally sparring over Kim’s alleged pro-North Korean ties and links to the NPAD.

Saenuri Party chairman Rep. Kim Moo-sung characterized the attack as a pro-North Korean leftist’s attempt to break the Korea-U.S. alliance. A party spokesman even went so far as to call the NPAD a “jongbuk host,” describing how the NPAD has long been associated with pro-North Korean personalities. Jongbuk, a term originally used to refer to followers of North Korea’s ruling ideology, is now used broadly as a blanket term to describe pro-North Korean elements.

NPAD chairman Rep. Moon Jae-in shot back that politically exploiting the incident by defining it as a crime committed by pro-North Korean forces would not help Korea-U.S. relations. At the same time, he condemned North Korea’s response to the attack, warning that such an attitude could further worsen South-North relations. Pyongyang had called the attack a “deserved punishment for the warmonger U.S.”

On Monday, lawmakers of both parties continued the verbal duel, with the Saenuri Party attacking the NPAD for its alleged ties with leftists and the NPAD demanding an official apology for calling the party a “jongbuk host” and warning against McCarthyism.

Meanwhile, the police who detained Kim Ki-jong on March 6 on attempted murder charges are focusing on whether he broke the National Security Law, maintaining that such an investigation is part of the effort to discover the motive and forces behind the attack. However, concerns are being raised that the investigation is biased toward applying the security law in prosecuting Kim, especially given President Park Geun-hye’s order to find those behind the attack and the Saenuri Party’s assertion that the crime was committed by pro-North Korean forces.

While Kim has so far denied any ties with Pyongyang, authorities have found several publications judged by a panel of experts to be pro-North Korea. The police are also investigating a possible link with a spy ring that was nabbed in 2013. Kim, who claimed after the attack that he wanted Seoul and Washington to stop their annual joint military exercises, which he said stood in the way of national unification, has told investigators that there is no leader in South Korea who measures up to Kim Il-sung, according to the police.

The authorities should prosecute Kim to the fullest extent of the law. A thorough and unbiased investigation should be conducted to discover the motive and forces, if any, behind the attack. But the authorities should realize that attempts to bring spurious charges against Kim in order to prosecute him under the National Security Law could backfire. Applying the law, which the U.S. has repeatedly criticized for its potential for abuse in suppressing political opposition and freedom of expression, when it is not clearly warranted could have the unintended consequence of creating difficulties for Korea-U.S. relations.

Politicians should have the interests of the nation foremost in their minds. Bickering over ideology for political gain at the expense of national interests should not be condoned.