Honestly, I can understand ML here. ML and MC have been friends for over 11 years. And yet, he doesn't let him in on his private life and doesn't share things he should. Like why he couldn't contact him and stuff like that. It's not necessarily too much from ML's side. Because he wants to get closer and understand him.
And that line MC said was very hurtful honestly. I would have thrown a fit if I were jihyun
"I'm your manager"
It makes it sound like he isn't his friend but just his manager.
And it definitely makes ML look like a bad person who kept him busy than actually meeting his "lover"
So, in my opinion, ML has a valid reaction here.