The original question was should young men and woman ages 18-20 who serve in the military be allowed to consume alcohol. The question was vague however most would upon looking at the original question think it dealt with drinking here in CONUS (Continental United States). Deployed outside the Continental US it's a non issue for the military, because Command directives will dictate who, where, when one may consume adult beverages.
The oath you take upon enlistment says your going to obey the orders of those appointed over you. When you serve you give up certain rights. That's the nature of the game. You want to play, you got to pay.
18-20 year old military members are no different today then in past years by and large.
When I was stationed in the 101st back in 77-79 the drinking age was 18 years old, I was 18 years old so I had a few beers from time to time. We had problems, but they were no more different problems then in 1997 then when I was a First Sergeant in the same Division years later.
You should not make laws for the few who cannot accept the responsibilities of adulthood. Play stupid games, and win stupid prizes.
The list goes on and on.
We should control guns because some people uses guns in the an unlawful manor.
We should restrict free speech because some people say hurtful things about others.
Freedom is about being free to make choices. Every time some law is passed it's often passed to restrict someone's freedom. I say let freedom ring. Let those who are unable to act in an adult manor pay the price for making poor choices. Don't make the vast majority pay for the actions of those unable to conduct themselves in a grown up fashion. Adulthood requires people to conduct themselves as adults and accept responsibility for the actions they take.
I found it stupid that my son who upon graduation from Ft Knox KY and Armor School as an M1 Abrams Crewman could not have a cold beer with his Retired Airborne Infantryman father. We did not have that cold brew because we are adults and we made decisions based up right and wrong, rules, laws and regulations. Still did not make it any less stupid.
Like I continue to say. My opinion is my opinion. Others may see things differently.