
Every bad people are raised to be a villain that doesn't excuse of the bad things they did. An examples are killers, they have a reason why they are the way that they are but it doesn't excuse them for being killers, are they? Just like he is, he is still the villain.
Also, Reading comes with connection and comprehension. Everyone understands that it is fictional, everyone does however connecting to the story is important because it lies on how you understand the story, and how you connect with it. That is partially why you have your own opinion on this story because you try to understand it with your own moral. In every story it is important to understand the characters, and how well-rounded or justifiable they are. People using the excuse that "stories are just fictional, and we do not need to dig deeper to it" is just a lazy excuse to not think about or connect with the story.
Just, what is up with all these people? Sympathy? Emphaty? You want Jaekyung to have rehab? If you were on his place what would you do? Try to put yourself in that situation, if you choose to be kind and end it then freaking do it. We're here to read it and not to justify them AS a person. They're fictional. Sadly, of course people are like this and we'd have to understand them. But make them look like the villain is outrageous! He wasn't born to be a villain, he was raised to BE one. And that's different. Sure, every top in yaoi has this thing about being a psycho and having a deep back story; The thing is, not all people are the same. Not all of them wanted to be who they are now. They're traumatized, and rehab is something you can make out of your own choice. Trauma, isn't easy. Being afraid of almost everything, isn't easy. Being scared, being haunted every second, every where you go you are being followed by your past, it's bad. It feels freaking tiring, it's like your life ended when it was your turn. He is who he is because of what happened in his life. You are who you are, and you think that way because you weren't the one who experienced it. You are who you are, because he is NOT YOU.