I have a ton of thoughts on this thread and different ideas and comments I've read, but I'm so late to reading the thread I don't even know where to jump in here.
I think something that does stand out to me is a desire to say that I truly feel sometimes some people can't see that "one size fits all" does not (and can not) apply to every adult difficult child (or easy child for that matter). Missing from so much of this topic is the individuality of each parents adult children. Different things work for different people.
My Matt? He was on the wrong path and nothing I said or reasoned or dangled was going to move him in a better direction. Nothing a third party could tell him was going to affect change for him. For him, what changed was that even at a young age (11-12), I removed him from our home. My one requirement to come home was to be conducting himself in a manner within our family that did not harm the emotional (or physical) well being of us here in the home. That he must participate as a family member, not a terrorist in our home. Period. Full stop. It killed me to have him saying I was "throwing him to the wolves". And I can say with honesty it took some time for me to look past the harsh judgmental opinions of outsiders. I had to remind myself that outsiders did not know MY son as a human being, a individual with his own motives, dreams, anger, frustrations, skill set (and lack of in many cases). I just kept my mind focused best I could on MY particular child and for us it turned into the best decision ever made. Popularity or disapproval of my "way" aside. It worked for my difficult child. He eventually hated the life he was leading, the loss of the cornerstone of his life (family and the only home he ever knew) became something that for him he wanted back. What must he do to get it back? Be a healthy contributing member of our family. So he came home and proceeded to make choices that helped meet that goal. Eventually he learned that when he struggled with decisions he could come to ask for guidance and would not receive criticism, but he would receive honesty. I stopped at the time I removed him from the home, giving him any unsolicited advice. I did however tell him he can always talk to me if he wants help to make better choices. Left to his own devices, he did exactly that. Now at 18, he has moved clear across the country, a 4 day trip away from "the nest". He is motivated, mature, capable of making healthy choices (or asking for guidance if he is unsure of a situation he finds himself in). He realizes he has a place in a family and society but also that he has a responsability to both family and society. And he learned he doesn't get the benefits of being in the "bosom of the fold" so to speak, when he acts in manners that makes him a undesirable member. He knows he will always be loved, but that nobody is going to jump on board his sinking ship with him if he chooses to put a big whole in the bottom of his boat. He is the captain, he'll only have passengers if he keeps the ship floating. Otherwise we'll lovingly be waiting offshore for the day he fixes his ship. And that he can ask us for advice if he doesn't know how to fix it.
Having said all of that, would this work for others? Perhaps. Depending on their own childs personality. Also depending on the age, situation, etc. I do know this approach, had it waited until now at his age of 18? He would never have responded that way at this age. He would have walked out the door and continued a downhill spiral. I caught him at an age where others sometimes criticized me harshly but at the perfect age/time for HIM. He also had no drug or alcohol addictions, he was able to be AWARE of his harsh impact on others at the time (even though he refused to gain the skill set to change his anger/rage etc). But what if he had addictions at that time? What if he hadn't been aware of his impact on others due to inability to see outside of himself? This approach I used likely would have not worked at all. I can't say what I would have done if he had those addictions or lack of awareness. What I can say is that the approach I went with likely would have not been handled the same way at all.
I do know a common thread all of us parents on this board have, is a desire to see our children grow and mature and thrive, move into adult life with a good skill set, good healthy values, something to motivate them towards a good future etc. As clearly as I know that we all share that common bond, it is equally clear to me that all of our children are so different and therefore our approaches must too be different. There is no magic answer that helps everyone equally. The beauty of this board? If for example some members difficult child appears similar in personality say, to my Matt. Well I can then explain how I handled things and what the outcome was, and why it was right for my Matt. At the same time, I could offer advice similar to my own approach my Matt, but I may be completely wrong in reading posts and that persons child may be nothing like my Matt in personality and motivations etc at all. In which case, my advice might even come across as callous, as if it is ludicrous to suggest giving them the toughest love approach possible when clearly it might make their situation worse instead of better.
I guess I just hope that we can learn one thing on this board above all. That the beauty of this place for us to come discuss our children (minor or adult children), is that with so many differences in situations and personalities of our children, we are bound to learn from each other and better see what choices we might make that would work for our particular children. This board has taught me to dig deep with my difficult child, analyze his person, analyze what works or doesn't but more importantly WHY it works or doesn't work for MY particular child. Cookie cutter pod people our children definitely are not. I have also come to learn a great gift (in my opinion). That when our children grow to adults, we have to learn along with so many other things, when we reach a point that nothing we can do (or not do) is going to "Fix" our childrens problems. I think it is key to know when to stop. When to live and let live.