I think the issue is moderation. People aren't all that good at moderation --which is why you don't get doctors encouraging people to have "a moderate amount of red wine" because people will make up their own minds what "moderate" means even if you say 4oz... that definition will be stretched.

I knew [past tense] some coke addicts, not pretty.

Alcohol is not "good" on the other hand its effects usually take a decade or more of heavy use to show up in most adults-whereas heavy use of other drugs ravage people quicker.