I haven't been around much the last couple of days, and just came across this thread. Here is my view.
It has already been said, but I will say it again. When a person has any kind of problem, be it substance, or psychological, and does not want to get help, and then ends up hurting others due to their problem, there is nothing you can do. I've gone through this, especially in regard to psychological problems, with other relatives and friends, and no matter what I tried, patience, suggestion of therapy, threats to distance myself from them if they did not stop the destructive behavior, nothing seemed to work. Eventually, as painful as it was, I had to distance myself from it, for my own well being. It sounds to me that, despite all the pain you have over this problem, this individual does not want to help themselves, and wants to be destructive to himself, and others. In such a case, even though it may sting greatly, you should distance yourself from him, for your own well being, unless he gets help, and changes his actions. It does not make you cold. Self perservation is the first law of nature, except in cases of your children, or perhaps immediate family. Otherwise, if you are going through so much pain by dealing with him when he's like this, as painful as it is, distancing yourself might be best in the long run. Hopefully, he will see the light of day, and want to do something, for himself. If not, then that would be most regrettable, and it would show he holds such little value for both himself, and his friends, that he isnt worthy of your friendship if he's like that.
I pray he can do an about face and help himself. For his own sake, and those around him. Unless he does, distance might be the best option.
Mitch