Ok Este, which is it. Were there no cops or the the FBI pre-police the event? The way I'm reading it, you're finding it a problem that there weren't enough police. And that it's a problem when police are there because Nazis would have made Richmond descend into violence and fascism, the police wouldn't have rounded up the Nazis if they were there, but they already rounded up the Nazis before they were there.
Been at a lot of random events where lots of people have guns. Big sporting clay shoots. Good high school sport, that. They aren't normal events because of a primal fear for life maintain manners, they're normal events because they're normal events.
Funny, I regularly attend events of 100+ people where literally every person there has a pistol on one hip, and several (usually high-capacity) magazines on the other hip.
Sidenote, there's a safety briefing at the start of each event, and they note that if there is any sort of firearm-related injury, do not call 911 and report "someone has been shot", as it will bring in police with guns drawn (and the image of them arriving and being casually surrounded by dozens of armed bystanders - most of whom are considerably better marksmen than the average cop - would be comical if it were not so serious); rather refer to it as a "training injury", and the local dispatcher and PD will assuredly understand.