Its so tempting isnt it, to imagine yourself telling his friends, family etc why it is you left or threw him out as you know your Alcoholic is telling a completely different version of events, the one where he gets to keep his dignity, and I agree with the others, but you have to take the high road on this one.
They wont even admit to themselves that they are Alcoholics so why are they going to confess to someone they consider a friend, that they are alcoholics who arent fit enough to maintain a marriage. Of course they are going to blame shift and say they left a nagging wife. Allow him to find his own path to recovery. He may well outstay his welcome with this friend and do something outragious and will have to face up to the embarassment of loosing another friendship - who knows, but mind your own business as they say at Al-anon. I know its tough but I say this to myself often these days.