Responses
He's not homophobic at all. I remember that they're all still friends even after telling them about their relationship. I admit that I was weirded out too by his reaction which borderlines jealousy but aside from this incident, there's no other indication that he likes Jiwoo. All I have ever felt from his interaction is that he is naive simpleton that is a huge fan of Jiwoo.

a. He’s homophobic and can’t handle being on the same team as someone gay?
b. He’s also gay and just realized he should have been dating a guy instead of worrying about what everyone else might think?
c. He’s furious that his “friends” kept a massive secret from him?
None of the above? All of the above? I need answers immediately.