The ruling reinforced Washington's strict privacy act, which says that consent from both parties is required to listen in on telephone conversations — even if you suspect your child is involved in a crime or is in danger.
Before you are 18, you have no privacy rights.
Aristotle, was your comment a statement of law or of opinion? If it was law, then I don’t understand the ruling from the article in question. If it was opinion then could you make your case?

It seems to me that if I had an 18-year-old relative who was behaving in a way that made me suspect something was going terribly wrong in their life, then I would be just as likely to intervene with that person as I would a 17-year-old or a 60-year-old, regardless of their privacy rights. If I were to read their diaries, eavesdrop on their phone conversations or burst in on them while they were showering or masturbating, I’d do so knowing that I might very well be destroying their trust in me for years to come.

A person under 18 might have no legal right to privacy, but I am confident that they would react the same way to the person who breached that privacy as a person over 18 would.