To the people with that attitude I'd like to plainly say that you don't know what you're talking about. At all.
Alcoholism in it's true form - physical alcohol dependency - is a terrifying and debilitating disease, that captures the very will of the afflicted. There is no escaping the siren song of alcohol for the sufferer. It isn't a question of "just say no", it's a minute-by-minute willful struggle against an urge so powerful that at times, the alcoholic would gladly trade the lives of his children for another drink.
The same applies to drugs like heroin. Unless you've felt the craving, the absolute need for more, a need that outweighs any rational argument against it, or can conjure up an ounce of imagination and understanding, then keep your pithy, profoundly unhelpful comments to yourself.