Looks like a New York Times columnist is making a reference to open carry rallies such as the 4-19 and 8-14 RTC’s here:
“There is nothing you can do about the crazy 5 percent except ask the police to keep an eye on them during large public events, where they sometimes appear carrying machine guns just to make a political point about the Second Amendment.”
Misinfo about “machine guns” etc. aside, I like the 5% estimate. Works for me.