We all have our demons. He is possessive but he tries to keep beom's interests ahead of his. You cannot tell me you never even *thought* of doing something evil but you end up not doing it anyway. He just thought it was the quickest way he could keep Beom safe and unharmed from the world. I don't think thinking about doing something makes you evil. Its just his good side and bad side debating about his thoughts. To some point I even think it's an innocent thought just in not so pure direction.
To the people saying they wanna drop the manga for this, it's your loss.
I rarely read bl for its plot and this is one of those rare mangas.