Drinking in public makes me uneasy as well. If it was just some guy having a beer in the park while walking his dog or at a picnic that is one thing. In places like London though, you get abject alcoholics just drinking a bunch of schwag then passing out on a park bench, a bunch of chavs huddled around some malt liquor and weed and just a general increase in poor public conduct.
I'm totally fine with lowering the drinking age, making it easier for places to get a liqour license and at least lifting the LCBO monopoly, but only as long as it is regulated to ensure that drunkedness stays where it belongs, pubs, clubs and people's homes, not parks, back alleys and sidewalks.