It's because in Korea women have been abused by men so much that it's culturally not taken seriously enough - so it's kinda what you learn.
Japan also had similar cultural problem with SA/rape, you can see it especially in earlier shoujo mangas towards teen girls, it was just normal.
In Korea, it seems it became more and more apparent that only way those women can actually have an outlet is BL manhwa, so it has gone way worse from the time this series was done. Korea isn't fixing their society problems while Japan has been actually trying, and you can see it in literature written by women.
And because Korean manhwa broke the tag system that helped a little to shield younger audience from all that stuff - then became the young new manhwa readers, that learned too early on that toxic relationships are normal. They maybe can understand that rape isn't right, but miss all the other SA and abuse signs because rape is the level everything is at.
It's really hard to relearn that shiet when you get influenced so young.
(Also, before anyone start to while that rape has always been BL/yaoi comics culture as some kinda defense. Yes, but it was very different reasons before, bigoted against gay relationship, and you couldn't show them in good light until culture evolved to be better.
Now it's because different reasons (revenge, etc.), but mostly by accident ends up being even worse to minorities.)
Why is there a weird trend of rape not being treated seriously when the victim is a man? Especially if he's on the bottom? It often feels like author will introduce this narrative as a blip and move on? If you plan to not go to an angst route with a heavy topic, then chose a murderous one...let uke get his lick back and beat his rapist to a traumatising point or even kill them at least ヽ(`Д´)ﾉ