Indeed, it would be senseless for the Chinese government to sabotage a relatively China friendly government in South Korea over some racist bars and cafes.
We must remember that within every society, there are different factions, and we should never confuse them for each other and in doing so, inadvertently give power to the enemy factions. That is what the right-wing supporters in South Korea want, ultimately - to sabotage the present government and stir up conflict with China.
They and their handlers in the West want to bait China into escalating and trashing relations - and the right action, here, is obviously not to bite.
This is also why I think the problem needs to be resolved at the grass roots level, not the government level. The Chinese population should organize and create a black list for businesses and owners deemed hostile to China - a hall of shame so to speak - that could then be used to "cancel" them on social media and to pressure investors, companies, celebrities etc. into not working with them.
It's this kind of pressure tactic that will have the most effect on isolating and containing those black elements to the fringe of global society, and make them pay without ever falling into their trap.