Alleged mass shooter Payton Gendron’s online screed trafficked heavily in this theory. He even labeled what Whites are facing as “genocide.” Amy Spitalnick is well positioned to discuss the role of these ideas in mass shootings and in broader ongoing white-power movements. She is executive director of Integrity First for America, which successfully held organizers of the Unite the Right rally liable in court for damages. That effort employed a new tool in the fight to break violent white supremacy. But what has followed since then has been profoundly dispiriting about how challenging it will be to prevail. Follow Greg...