This paper develops a structural framework for understanding deep disagreement, normative conflict, and the emergence of social tragedy. Rather than treating persistent disagreement as a failure of evidence, rationality, or goodwill, the paper argues that some conflicts arise from structural incompatibilities between non-negotiable commitments that constitute individual or collective identity. The core contribution is the Legitimacy Trilemma, a formal limit result showing that once a system acknowledges an internal violation of a universal, non-negotiable norm, it cannot simultaneously maintain universality, insider inclusion, and quiet tolerance. At least one must be abandoned. This explains why stable pluralism becomes impossible in certain moral, political, and institutional conflicts. To make this precise, the paper introduces a geometric framework that characterizes normative commitments along three dimensions: negotiability, target scope, and actionability. The framework is scale-invariant, applying equally to individual cognition (e.g., cognitive dissonance) and collective agents such as institutions, religious communities, or states. The analysis reframes phenomena such as exclusion, enforcement, censorship, and epistemic injustice not primarily as moral failures, but as structurally compelled “repair moves” undertaken to preserve normative identity under internal contradiction. The result is a tragic but explanatory account of why many conflicts escalate even when all parties act coherently and in good faith. This work is intended as a foundational, diagnostic contribution to social epistemology, normative theory, and the philosophy of disagreement, clarifying when disagreement is not merely hard to resolve, but structurally irresolvable without identity-level change.