One exercise to illustrate the ridiculousness and disrespect of phrases like that is to replace "alcohol" with "crack".
"I don't do crack anymore" would basically never be responded to with "you know, you could still have a little crack every so often!", so what's the difference? Some folks don't do alcohol anymore. And whether that's for health reasons, for "I'm tired of dancing on the bartops" reasons, or just for "I got bored of the scene" reasons, that's their business.