How the Tree of Life attack reflects American anti-Semitism

President Trump called Saturday’s synagogue shooting anti-Semitic and “an assault on humanity.” But a chorus of voices argues that the president himself has fostered a national atmosphere of hatred. William Brangham speaks with Jonathan Greenblatt, head of the Anti-Defamation League, and historian Deborah Lipstadt about social media's role as an amplifier and politicians who "embolden" violence.