That video footage is really fucked up. According to participants and organizers, the rave was completely legal and had all its permits in place. According to the Salt Lake City Tribune it was an 'illegal' rave where children were practically being forced to consume a wide range or terrifying drugs. Thus fully justifing groups of men in full assault gear and masks flying in in helicopters to kick the shit out of partygoers.
The one thing I haven't been able to ascertain is whether the armed guys were SWAT or National Guard. They are described as SWAT in the press, but their gear looks much more military. If it is the National Guard, are they even allowed to be used in that way?