The ADL stressed that its findings do not imply that the Republican presidential candidate endorses these messages, nor that he has encouraged people to send them. But Trump’s campaign is the looming context behind these tweets. As I wrote in September, “Trump has passively cheered on anti-Semitic trolls, appointed a man accused of denying the Holocaust as one of his advisers, and tweeted graphics that incorporate anti-Semitic imagery.” His campaign has attracted the support of neo-Nazis and anti-Semites; the rhetoric he has used to talk about ethnic and religious groups, from Mexicans to Muslims, has created space for all kinds of bigots to express themselves online. The free-wheeling norms of the internet haven’t helped; what was once considered plain old racism and bigotry has come to pass for trolling.