Personally I would prefer for alcohol to not even exist but it is incredibly hard to say what influence it directly has upon sportsmen/women.
Would Andy Greg have been better or worse minus alcohol. The textbook answer says yes he would have been better but would he? Perhaps he needed alcohol, perhaps he became dependent on it? I could find you a tea total more rounded, athletically scrum half and he would not be in the same class as Greg. I would much rather have a player with a huge heart, bags of courage and supreme tactical awareness who needded alcohol than a tea total super fit half back lacking heart, courage and tactical awareness.
Sports strips a man/woman 'naked' The true person is exposed in a way that perhaps only war exposes more. Even in war, 'enemies' rarely spend as long face to face. So is sport as simple and clear cut as the Dave O's of this world like to believe. Nothing is ever as simple and as clear cut as we think.
Alcohol I wish it did not exist and then the cost to our nations would be far less BUT where do you stop? I

at the hysterical reaction to the Olympics in terms of sport in Britain when actually physical exercise lessons would offer far more benefit to this country than competitive sports lessons ever did in terms of health.