People who do not much like each other will cooperate when they share a goal that neither can reach alone. That is why a hockey team defends its least popular player, and why campers of every age unite behind Color War. The same tool builds fear-based movements when a leader points it the wrong way, so it deserves care. Use it to bring people together and never to set them against someone.
This is the short version. The full lesson, with the story behind it, is in the book.
Take The Summer Camp MBA with you, or get the field notes by email while you work through the lessons here.