Principle: One should criticize the works or actions of another person only if the criticism will not seriously harm the person criticized and one does so in the hope or expectation of benefiting someone other than oneself.
Principle
Criticism will seriously harm the critiqued or → Don't criticize Not hoping to benefit other people
Application
Jarrett shouldn't have criticized O, because the defects in O's essay were so obvious that pointing them out benefited no one.
Evaluation
Since the application is trying to conclude that J shouldn't have criticized, we want to look at rule (contrapose if needed) so that "shouldn't have criticized" is on the right side, where conclusions go. To justify that conclusion, we just need to establish one (or both) of the criteria on the left of the arrow, since it's an "or" rule.
the critique seriously harmed Ostertag or Jarrett had no hope or expectation that the critique would benefit someone else
Goal
We know that the critique benefited no one, but we would need to know that Jarrett had no hope or expectation of benefiting others. Or we need to know the critique seriously harmed Ostertag.