
He’s a bad person because he made it clear he was only interested in casual sex at the moment and the person he’s doing it with is gladly accepting it? I’d say it’s a bigger matter of Yeonwoo lacking self respect rather than Taehwan being a bad person. He’s never abusive or anything to Yeonwoo, which is the bare minimum, but still. He started off being rude to him but that’s because Yeonwoo severely screwed up their relationship by taking advantage of him while he was vulnerable. So it’s no surprise that he put clear walls up and wasn’t openly accepting him with empathy and joy, especially since they started hooking up because, once again, Yeonwoo pounced on him (granted he was drunk this time). Despite all that, he’s visibly getting more open with each chapter to the point where he held him close during their hook up and joked with him when he got his clothes dirty rather than getting upset. Having emotional walls up for someone that wronged you doesn’t mean you’re a bad person, and the fact that we can see his process of those emotional walls breaking down proves that he’s not a bad person and that he’s just someone that has a difficult time opening up to people.

my point: there are not only walls, he is not defending himself but he is deliberately hurting people by treating them as if they are disposable, with contempt and harsh words, making it clear that he does this outside the sexcen and with other people around him.
Yeonwoo being wrong or agreeing to be mistreated during sex for loving this idiot does not change my point, RESPECT is missing. They both agreed to this relationship, but if he doesn't want to have the slightest regard for someone else then let him move on.
And you are romanticizing him because "he is visibly getting more open" while demonizing Yeonwoo for past mistakes, which we know were impulsive and based on true feelings, for God's sake he was a passionate teenager who made a mistake not a rapist.... but keep acting like Taehwan is the only one who deserves to be understood

"He's never abusive or anything with Yeonwoo"
fucked him without looking him in the face, like a disposable toy; called him out for his sexuality; left him tied for hours without surprise with a chance of being discovered; threatened in a violent way (shouting, pulling and shoving); pretended he hadn't existed for years but now that he wants sex he's back ...
Taehwan is cold and not very romantic when he’s with Yeonwoo, but it’s clear that he’s been through some really disgusting shit that makes him act the way he does. I still think Yeonwoo was super gross and creepy when he kissed his clearly emotionally exhausted and dejected friend while he was sleeping and finally felt comfortable enough around someone to relax and be himself. That doesn’t excuse how he’s kind of dragging Yeonwoo along and not being necessarily kind to him or warm to him when he’s clearly using him for a physical connection, but his behavior is not even close to bad enough for him to deserve to be considered a bad person, especially since everything he does is done with Yeonwoo’s eager consent. I’d say the worst thing he did was leaving Yeonwoo tied up with sex toys for a long time while he went out with friends. There should’ve been some MAJOR aftercare after that, but he’s continuously getting better and more open (at least with his body) despite there clearly being some childhood sexual trauma going on, and feeling like the guy who he’s doing all this with took advantage of him while he was finally being vulnerable.