I think that drinking as a whole is bad. Now if this is done at your own home where you will not be on the road, then I'm fine with it. If it's done at a bar and you have a ride home, then that's also fine.
My biggest problem is people who drink, are of age, and they get behind the wheel and drive. There have been too many accidents and deaths from intoxicated drivers. This needs to stop.
So I don't really think that underage drinking is a "problem." What is a problem is people who can't handle their alcohol and if they are irresponsible.