They're best friends so that means they should understand each other. As someone closest to him, he should know Woojin is not the type of person to do that.
Also Ho-in's first instinct was resorting to violence before talking things out. If it weren't for Woojin's reflex, Woojin would've gotten a knee directly into his face over a misunderstanding that could've been easily cleared.
I kind of agree. Because in normal situations, that would be the case. But before that scene finally happens, a lot of events preceded it, especially involving Woojon. And that builds up the frustration in Ho In. And that's why he's totally irrational when he catches them together. Tbh I think he's just been itching to beat up Woojon lol, cuz he keeps occupying Sunbae.
And also as said in this episode by Woojon himself Ho In breaks his own rules if it's related to Sunbae. So more than anything to do with their friendship, you can just say he reacts differently in anything that involves Sunbae.
That's my understanding at least. I could be wrong.
Idunno I've literally heard of stories IRL of lifelong best friends cheating with spouses and shattering lives so if he's seeing a lot of things that easily give you a misconception, ESPECIALLY after everything Ho-in went through to even be in that relationship, I'd understand why he's lose his cool.
From what I'm hearing about the spoilers... I mean wouldn't you feel EXTRA betrayed if the person you thought was closest to you was caught in a compromising position with your lover?? Like people are saying why would ho-in hurt his best friend who was nothing but kind but I think that's exactly why if he really thought something was happening that he would react so horribly.