Shared hatred of a common enemy powerfully binds people together.

Evidence

In general, common enmity is one of the most powerful means for motivating a number of individuals or groups to cling together. This common enmity is intensified if the common adversary is at the same time the common ruler. — Georg Simmel, The Sociology of Georg Simmel, 5126

Categorization

• XREF: connects to: Hatred unifies with its object through destruction, mirroring reconciliation. — Theodor W. Adorno, Max Horkheimer, Dialectic of Enlightenment, 159