You're ostensibly incorrect because China is a member of the WTO and can't unilaterally start economic sanctions against other WTO members.
I'm no expert but a particular kind of music (k-pop) is more cultural than anything else and so it may be one of the few legal options China has.
Countries can and often do unilaterally break portions of global trade deals, and don't care unless there's action taken against them.
Oil producing countries are in a full blown international cartel, but does anyone stop them? Nope.
Is China going to get hit, whilst they're producing so much of the raw materials needed for electronics?
I see you're trying to cast a hypocritical light on the US, even though the US has nothing to do with it.
The complainants (Antigua and Barbuda) were compensated in 2014, by the US.
Ultimately a country can build a case for banning a thing (a good, service, etc.) but if a country says 'These widgets are OK, in fact we manufacture them ourselves, but we've decided to ban the ones that come from country X' then that usually is anti-trade in no uncertain terms, in WTO language it is 'unfair.'
It's not like the US banned online gambling on purpose so as to try to cripple the Antiguan economy, as would be the case for banning Korean exports to China.
From the article:
> Why? .... South Korea made the decision to deploy the THAAD American missile defense system in the country
They are responding to increased military tension with their neighbor, with a minor economic sanction that will not hurt the health, welfare, or stability of their neighbouring country.
Such sanctions are a warning shot---a way of saying "yes you see what we did to the pop industry? we can do that to your heavy mining industry next".