Violence is one thing (although I do abhor it too), and it is expected in action dramas, thrillers, horror, and sageuks (either wounds or torture).
But when we're talking about abuse it's a less well-defined thing. As for instance in a couple, in a teacher-pupil relationship (I've done a lot of online research on physical punishment in Korea, the situation is still appalling in many places) and abuse from parents to children which in k-dramas is pictured as "normal", "funny", "an expression of love and concern" (really?)
I don't know if you've watched "Another Oh Hye Young". Beautiful drama, by the way, I warmly recommend it. Well, the heroine's mother was shown as loving her to bits, and yet she was extremely abusive. It was not just an affectionate slap on the shoulders, it was really beating her up. And the daughter was in her late 20s or early 30s.
In "Five Children", we see a mother in her thirties shown as very tender and loving, with a wonderful relationship with her son. Yet, when he does something she deems inappropriate at school, she takes out the cane and he prepares stoically to endure the caning of his lower legs. And another mother, of a 35-year old son, also gives him a strong beating when she discovers his girlfriend is pregnant.
Same in "Father is Strange". These are not action dramas, but romance and family dramas!
One doesn't mind violence so much when it comes from a murderer, a heartless noble in old times punishing his slaves, a soldier, or a person taking revenge for the murder of his loved ones...
I mean, I still don't like watching it, but from this kind of character it's expected and understandable, so, although it disturbs you visually, still you are not surprised or appalled in the same way as you are when violence is condoned and expected, done by a supposedly loving parent or an educator of the 21th century.
You get the difference, don't you?