To be fair, he threatened him thinking it would scare him off since his awful ex is lurking around .
Thing is, if he doesn't quite act like this then in ML's reasoning they have no reason to see each other. For ML, MC isn't even a friend but just a responsibility he has to get through, cuz of his childhood.
The main reason why ML even kept pestering MC is cuz he thought it was his responsibility to "fix" him.
MC knows that if he confesses he'll just be rejected or even pitied likely, and that it'd be the end of their already non-existent relationship (cuz again, ML doesn't seem to even consider him a friend).
So, he'll keep being "bad" so that ML worries about him, while making passes at him to break down his poker face and make him think of him.
It's a terrible approach, but I understand the reasoning behind it.
Also, like the person above me said, it started cuz he wanted to keep him away due to his ex being dangerous.
ohh thats another perspective i didnt think of haha
lowk the kiss threatening part is kinda unnecessary, bro cldved js told the man outright that he liked him but he decided to threaten him to go away instead with sexual harassment.
but maybe the author wants to add in more angst. like the mc realises his actions overlap with his evil ex's and then he goes full panic mode and nvr speaks to ml again cuz he feels bloody guilty. i lowk cld see that happening for plot. idk js my deduction with the events going on in the story. but i feel that its rlly unnecessary if this plotline doesnt happen