I tend to be an all things in moderation type of person. I don't drink or use drugs of any kind. In fact, it's a rare occasion when I am willing to take an aspirin for pain. However, I don't think that my choice not to take or use these things should have any weight on your choices.
I have grown up with and around addiction, my father, grandfather, and husband have all struggled with addiction, and know first hand the damage it can do. However, I feel addiction itself is not a reason to feel negatively about alcohol or drugs, as many other things - food for example - can be just as addictive yet carry no negative connotations simply for being what they are.
To me, if someone is of an age to understand the possible consequences of their actions and they aren't putting others in danger (driving while intoxicated, etc) no one should have the right to tell them they can't do it. It's your body, and if you choose to use drugs, alcohol, fatty food, cigarettes, or whatever else to damage it - that's your choice! I won't be joining you, but I won't be hold it against you either.
Now, all that said, I feel there is a difference between using and abusing. In moderation, I see no issue with drugs or alcohol. I have a big issue when it goes from wasting some time on the weekends getting high or drunk, and becomes a way of life which stops you from living... For that matter, if you're one of those "functional alcoholics" it's none of my business how often you drink - as long as you're not driving. But when your drinking issues mean you can't hold down a job, pay for your own apartment or support your family - then there is an issue. And again, I feel this way about ANY addictive activity - be it drinking, using drugs or shopping!
So over all - All things in Moderation with common sense and keeping the welfare of others in mind.