The principle
People have an overwhelming desire to believe in something. Become the focal point of that desire and you will gain followers who will defend you against anything.
The application
A vision that is large enough to organise people's identity around binds them tighter than any contract. Cults, movements, brands, and the best startups all run on this. So do the worst.
The defensive tell — how to spot it being run on you
When a leader's appeal rests on a vision so large that disagreement starts to feel like betrayal, you have left strategy and entered religion. Hold whatever distance you need to think clearly. The belief is sticky; the costs of believing wrong are paid by you, not the leader.