I'm flattered you said I was using a "hippy argument". When I was 18-21, I was the biggest Ronald Reagan fan, conservative, crew-cut high and tight kill 'em all gung-go type you've ever seen, who was either in school, working as a lineman at the airport, or downing some longnecks with my friends after work. Anything but "hippie". My favorite song was Merle Haggards 'okie from muskogee'.
People are going to be responsible or not regardless of a drinking age law. Draw the line wherever you want. I don't know of ANYONE who wanted to drink, but waited until their 21st birthday...and that's a LOT of people!