Not sure what to make of this. My initial reaction was that they’re trying to ban a specific type of person, but then further reading does actually imply something happened that was directly related to the wearing of these clothes…
No Dr Alan Grant costumes for Halloween then…
It sounds like some sports club has taken to wearing a “uniform” which makes it easy enough to spot them. You often have look at the rugger buggers for bad behaviour - I know when I was at university their bad behaviour was legendary. They once attended a beer festival en masse with big parts strung round their necks dipping a trotter into their pint before necking it.
edit: although you’d imagine they’d just change clothes, but they may be too tied to some made up ritual to do that