The occasional drink won't hurt anyone. The fullblown night out will set back a bodybuilder, as will any regular drinking.
Alcoholism is basically taking regular drinks, becoming a habit, not breaking it, and continuing into a downward spiral. In a normal person, THIQ, or TetraHydraIsoQuiniline, increases in the brain as you progress. This chemical is a trigger mechanism for addictive behavior and cravings. When I was in school for this last, they said it never leaves the body, and lies dormant in the brain when you quit using your drug of choice. When you "relapse" (drink again), it is immediately stirred up, and you're right back where you were, right down to the time of day and amounts you used to use.
As I said, regular people. There are certain types who take on a different kind of alcoholism that has no "cravings". They fall into destructive behavior when they drink, uncontrolled, and may only drink a few times a year. But when they do, they tend to wreck everything they touch. They are still classified as alcoholics, and may simply have different triggers that make them "need" to drink when they do. IMO, they don't have any or as much THIQ keeping the cravings alive daily, but that's just my observation.
Now that I'm almost 54, I don't need to drink to get a hangover. I have about 3 a week just from work!