It's a house party. Maybe loud, but still. I never did it, but I've had plenty of underage friends drink and party. I dont see the big deal, outside of driving home (if any of them actually would of driven); its just a party. Our parents partied, their parents partied and got arrested. No reason to mug him over something that is common and a "desire" of most teens at that time.

But maybe because I live up here, drinking is common and is generally accepted. Just dont get shit-faced wasted and try and drive home. Friends take care of friends, generally and wont allow another wasted friend to drive home.