This is my essential problem with Magnus’s actions. What is he going to walk out of every tournament where somebody who cheated at 16 plays in? Is that how we as a community address the problem of cheating? Passive-aggressive gestures against people caught for cheating in the past that pull uninvolved people into your drama?
And only do that after losing... Which is the part that makes him look bad. On other hand I don't think there is a way to look good in this situation. Other than just to shut up and play.
Why does he need the benefit of doubt though? There's no evidence or indication that he cheated.