Responses

In their minds, they just messing around and bullying him because it's an all-boys school and he's one of the few boys who looks as cute as a girl and they're harassing him as a form of fun. Ginger himself doesn't even realize the reason why he bullies him in such a way is because he's subconsciously attracted to him but hasn't discovered his sexuality yet, all he knows is that he feels upset whenever he sees Iltak happy with Hyungwoo.
Keep in mind people, being gay is a death sentence in high school in Korea so of course he trying so hard to keep that closet close.