First of all, if you want people to realize what they did wrong don't physically attack them and angrily scream at them. It doesn't work and only makes things worse.
She could've used the friend from earlier in the chapter. He actually knows about his situation, YuYang talks with him about his problems (as shown in chapter 84), even when he's not very open about it in general.
He didn't realize that what he did was wrong because somebody punched him. He realized it because he's never seen it that way and this was the first time somebody has every told him that.
If the friend had told him, he would've come to the same realization (again, punching someone in the face is not a good method, talking about it is way better) and it would've been more plausible and not that forced.
But then redhead wouldn't have looked that good and there would've been no justification for that couple to be important enough to take up all those chapters. He still would've been as unpopular as before, which would've been a problem once he becomes one of the leading characters or even the main character of the story (the story of the first couple is almost done now, if she doesn't manage to make the fans like him now she could lose many readers when he becomes the focus of the story).
She already wrote all those chapters about redhead, she can't switch to the guy with the grayish hair now.
I know right? aahh that was a good woke for yang. tho it's unfortunate for him that it has to be red, his least favorite person to tell him that lol but he deserves that for accusing him and punching him first xD I'm just a bit baffled that red seem to know yuyang's problem lol
anyway, I hope he can finally face LiHuan now.
God, what a relief, painful but necessary. Here you have this guy that won't trust anything his love interest tells him, won't share his pain with his friends for advice, can't share it with his family for support, and is content to just suffer in his self-imposed little bubble of misery forever - how are you supposed to develop him out of this rut and move the story along? No wonder the author got stuck, Yang's a very difficult character to force forward. A punch in the face works nicely.