True! And we don't know how he got expelled. Maybe him getting expelled somehow connects to Woojoo that's why Woojoo reacted that way.
And I also understand Minjae he doesn't really know the red haired guy the only thing he know is that Woojoo is hanging out with an "expelled" person and thinks maybe he's a bad influence to Woojoo and how disappointed Woojoo's parents would be.