It isn’t one event, it’s a pattern. Talk to any Haunt employees—there’s an issue with rowdy crowds and violence towards actors and, at times, other guests too.
Anecdotally, there seems to be a lot of overlap between days with cheap bring a friend ticket deals and particularly poorly-behaved crowds. If you get banned from the park after having a fun, out of control night with your friends for $20, is that really so bad? Plus, single day tickets have ALWAYS been a way to get around being trespassed by parks—they may ban your pass and maybe even your email and/or credit card, but anyone can still go buy a single day ticket—especially when you have to do it at the gate to get your $20 BAF deal.