First of all, all he did was refuse to play the guy. He then said he can’t talk about it or else it’ll mean legal trouble. Second of all, there has been an investigation into Nieman that has shown he is a cheater in online play. He also admitted to cheating previously.

So no, this isn’t “Magnus lost and couldn’t accept it”. It is “known cheater loses the entire tournament and gets downright bullied, till they reach the world champion, where they play a perfect game”.