A stadium wave starts when a few people stand up believing others will follow. For a moment it looks foolish. Then the people next to them stand. Then the next row. Then it sweeps the entire stadium and everyone is on their feet. Nobody planned it. Nobody commanded it. The mechanism required only belief and proximity.
The same mechanism shifts culture. When 25 percent of the population came to believe that marriage equality was possible and right, something shifted in the culture. Not because of any one law or one institution. Because enough people started saying it out loud. Because they made it thinkable. Made it repeatable. Made it possible for others to believe it too.
The argument is not that shared belief is automatically good. The argument is that shared belief is how humans coordinate at scale. It is the lever. And levers work in both directions. What matters is what we use the mechanism to build.