This article investigates how disinformation circulates on social media as adversarial narratives embedded in identity-driven controversies. Empirically, the article reports on the flat Earth echo chamber on YouTube, a controversial group arguing that the earth is a plane, not a sphere. By analyzing how they weave their arguments, this study demonstrates that disinformation circulates through identity-based grievances. As grudges intensify, back-and-forth argumentation becomes a form of knowing that solidifies viewpoints. Moreover, the argument resists fact-checking because it stokes the contradictions of identity work through grievances (pathos) and group identification (ethos). The conceptual contribution proposes a two-phase framework for how disinformation circulates on social media. The first phase, “seeding,” is when malicious actors strategically insert deceptions by masquerading their legitimacy (e.g., fake news). The second phase, “echoing,” enlists participants to cocreate the contentious narratives that disseminate disinformation. A definition of disinformation is proposed: Disinformation is an adversarial campaign that weaponizes multiple rhetorical strategies and forms of knowing—including not only falsehoods but also truths, half-truths, and value-laden judgments—to exploit and amplify identity-driven controversies. Finally, the paper has implications for policy makers in handling the spread of disinformation on social media.