TW, my 24-year old AS is also very articulate and bright. The only problem is that their reasoning get rather messed up with drug use and whilst they think they understand the world like no one else, their challenges of what is are rather old and incoherent at times. My son went as far as justifying his growing of magic mushrooms by pointing out corrupt politicians! He almost convinced me. If I was a counsellor, I would discourage any such justifications in group settings too. This may be what happened to your son.
I was reading Larrylive's journey on the addiction forum and he started off sounding just like my son and as time progressed, he sounded like a normal, wise human being. He really, really gave me hope for my own son and the recovery possible when an addict puts his mind to it.
My son also refused to go to rehab and he "knows" so much more than anyone else. I finally realised that it is simply a sign that he is not ready to admit that he has a problem and that he is not prepared yet to get all the help he can get. He also doesn't have a way to support himself but I finally had to tell him to leave. He needed to experience the result of his addiction and not use me as a safety net anymore. It has been 3 months now and I know it was the biggest gift I could give him.