Responses
I don't say that Mu shouldn't be mad at Song, he has the right to be, but you also need to see Songs situation. He left him alone for several weeks, but he loves him and wants to make up for what he'd done to him. You have to consider that Mu lives in this city only for his studies, when he is done he'll be gone (remember that call?), and then the chances to get together/make it up to Mu will be next to zero. So time really is a problem on both sides here.
Mu has every right to be angry at Yuanxun. Yuanxun treated him like trash in the beginning and then basically cat fished him. He deserves the cold treatment. I do think Yuanxun needs to give mu some space and time though. I get that he wants to make up for lying to him and show him that he was sincere but with something this big it's going to take time. I do hope he eventually forgives him though, I'm not saying Yuanxun was not wrong for what he did but I do want to see them become a couple because despite their past it seems like Yuanxun is really sincere about his feelings towards my.