Responses
I also know it is wrong. But I think few chapters back, when he was scolding Seungwon right after he was drinking he made him swear, if he drinks again Seungwon will pay for the repercussions since he doesn't want to go to rehab. People forget a lot why ML did what he did. Seungwon also repeat after him, acknowledging he really needs to stop drinking. From ML pov, Seungwon is pretty much hopeless when it comes to drinking habit and there's nothing at this point he could do to make Seungwon stop
He had a severe addiction to alcohol and I understand the rage from ML because he back again drinking alcohol when he tried to help and heal him. Not saying him raping MC is justified but his feeling is, his action is wrong. Also, scolding MC won't work because he will did it again and again. Rehabilitation is one of the solution after all.