Nobody held a gun to Chanwoo's head to do it tho. He didn't even told him to, he just said "you can go if you don't want to" . He could've noped the fuck out (as i would've done) but he decided to do it
Remember MD is older, and more experienced. He had experience in control and manipulation. He knew Chanwoo was a rape victim that found is difficult to speak up and say no. look how he repeatedly says that chanwoo refuses to say the safe word. So he takes advantage and makes him do things he doesnt want to do, like the threesome, and slapping his face (a reminder of his abusive past). His slimy.
nah fam.. not a big fan of how he manipulated chanwoo. lol if he was angry / jealous he should of just said it instead of making him do something he was clearly uncomfortable with.