I've never really understood this...
I guess maybe I'm lucky, and maybe an exception, but whenever I told my friends I had stopped drinking , the reaction was always "good for you, man! But do you mind if *I* drink." And of course I never minded because other people drinking is neither here nor there, as it pertains to my drinking. My friends were always (and continue to be) supportive. Maybe it's because I am (and naturally my friends are) older than a lot of the people that seem to have this problem? I don't know. All I do know is that if I had a friend who thought they had a problem with substance abuse, I can't imagine being anything other than supportive if they quit that substance. Doesn't seem that difficult.
Never been an issue with me and my friends, and I don't care what 'acquaintances' think.