I don't know if it's my place to say this as a girl - that's why I'm sending this email to you and not to needsyirasshamayim.
He posted on the forum regarding his 16 year old son who was found groping the cleaning lady.
It could be I'm totally off the mark with what I'm saying - but I'm gonna add my two cents in anyway
As a girl who was molestd by her brothers, I think that he should take this incident seriously. He has other children to protect that he C"V does not want them to be affected by this too.
There is nothing that can replace the unconditional love a parent has for a child, but loving him means doing the right thing. I see that he obviously realizes that it is a problem - because he posted about it, but once his son's actions became physical and not only gazing etc. he must do something proactive about it. True - he's a teenager and might not listen so fast - but you will be saving him and all your other children!
I'm begging him - please! take your son to a different therapist if this one isn't working out. You don't want to land up like my parents are - stuck between their children... Not every therapist is the right shaliach. Discuss this incident with the herapist. See what You can do to help your son. But don't ignore it before it gets too late... Don't just say he's an addict - he needs help!