I've always been shocked at how hung up some people are about the whole "if you're over this line you're good to drink, totally moral, but if you're not, then shame on you!" mentality.
Don't encourage children to get drunk of course, because it can cause developmental damage and being younger they're more likely to do something dangerous while drunk, but at the same time recognise the likelihood that they will occasionally get drunk once they're past 12 or so. It's better to just accept this and say to your kid "if you end up drunk somewhere, call me for a ride home" rather than try to go overboard with morality and say "don't ever drink or you're in more trouble than..."
But just letting kids have drinks around the house is fine. I probably wasn't given a full glass of wine or a full beer until I was at least 14, but even as young as maybe 5 I was allowed a sip (mostly to see how gross beer was!), and from my early teens I was totally allowed to have a responsable drink or two with a holiday meal, or special occasion, etc. I got pretty tipsy a few times at Xmas, was embarassed at my parents poking fun at me and stopped drinking for the evening. I think it took a lot of the rebellion out of drinking, I never really drank to rebel.
I'm biased as well, because where I grew up the legal age to purchase alcohol (you're legal to drink at home at any age under supervision as far as I know) is 18 years old. I think the norm around my country is 19 though.
I think the idea that someone is adult enough to vote or die/kill in a war, but not to buy their own alcohol or cigarettes is insane.
Rant over now!