A teacher who sees two children in a fight has likely seen those children fight before. After seeing the same fight occur over and over they just don't care who started it. Figuring out who started it becomes a chicken and an egg situation.
This example from the article reveals an interesting point about passing judgment in general:
...judges in the actual legal system can repeatedly hand down real verdicts without automatically losing their reputation for impartiality
That is because judges rule based on a set of written laws which they interpret depending on the situation. Picking ethical or moral side of a situation has no such standard.
Perhaps the writer also missed the idea that the majority of people in this world do not like conflict. Having to pick sides creates conflict. They are not trying to be wise as much as they are trying to avoid something that makes them uncomfortable.
Arguments are not black and white. Demanding the people pass judgment over situation where they do not know all of the information, do not have a set measurement for passing judgment and most likely do not care is unwise.