Everyones getting worked up over nothing. Most cities have policies that allow people to organize and conduct activities on government property if the group is small, say under 25 individuals. Over that, you have to get a permit, show liability insurance, add the city as an additional insured, etc.
The fact this happened to a bunch of young carolers is sad, but the adult organizers should not be laying the blame off on others when it was their fault for not checking with the city prior to the event.
PERMIT DENIED.