We had a similar problem at a park on Memorial Day weekend. We had been at this park before, but not on a holiday weekend. This park had cabins, and those were the groups that were the worst. They had 10-12 people in each cabin and partied until 2-3am including music so loud I could tell what song it was and sing along from inside my camper, from 3 sites away. The campground didn't have any quiet hours that I could find. I don't think we'd go back there on a holiday weekend. When we visited on a non-holiday weekend after Labor Day, it was totally fine and very quiet.
The owner of the park in the OP was put in a rough spot too... one person vs a group of 50+ drunk people can turn badly very quickly. I would ask for a refund and then decide what recourse I was going to take from there.