That's a terrible parent, not joking in the slightest. If the parent's chaperoning underage drinking, I honestly would be pleased to see a cop show up there and arrest that parent. That is an abhorrent thing to teach kids--breaking the law is totally OK. Next thing you know, those kids from that party are watching their kids and kids' friends while they do lines of cocaine. The next generation, they're on meth.
Yes, I'm exaggerating and it's not necessarily like that, but it slowly creapps that way. I wouldn't be surprised if that actually was going on in 20-30 years. People keep saying it's going to happen anyway, so they accept it. It's why morals are going by the wayside so drastically in the world.