Having someone arrested is not "lack of moral fiber". It may be the opposite - the courage to bring a criminal to justice, testify against them, potentially lose his friendship... What the 17-year old did was vicious and clearly criminal.
Courage, as a word, stems from cor -- one's heart and innermost feelings, and so courageousness is the resolve to express one's heart.
Therefore, it is literally more courageous to confront an attacker directly and to express one's feelings honestly, than it is to run to the authorities, even when one is entitled to do so. It's more courageous to confront someone face-to-face, tell him how you were hurt by what they did, and communicate that you still care about him and want to be involved with his correction.
To say that "it may be the opposite..." i.e. it may be cowardly to directly confront someone who hurt and frightened you, is just bizarre and I suspect reactionary tough-guy talk. In what world would it be cowardly to confront and attacker and show both your vulnerability and your determination to work with him, but courageous (in any sense of the word) to send the police over to his house to pick him up?
