A referee and a teacher play very different roles in people's lives. Students aren't competing for "first place in class," they're there to learn.

The analogy is to show how knowledge of the mean of a population group does not preclude impartial treatment of any individual in that group.

Or to pick an example with with similar moral connotations: "It's my opinion that black people have higher blood pressure than Asian people on average, but I will treat every patient fairly."

Would this (accurate) opinion prevent a doctor from providing appropriate care to hypertensive Asian patients?