Decades ago, I was part of organizing against Operation Rescue. At a couple of meetings some people showed up who seemed off. No one asked them to leave, although we all agreed afterwards that they were suspicious. When we called the contact info they'd left, it was wrong numbers all the way down. The first time this happened we all agreed that we would call them out if it happened again. It happened at least twice more, to similar silence from those of us who felt uncomfortable.