The Christchurch massacre’s live-stream on Facebook — and subsequent spread across the internet — further illuminated social media’s hate problem that many have criticized for years. It left countries across the world scrambling to force tech companies to answer for their role in white nationalism’s presence online. On Wednesday, New Zealand’s Prime Minister Jacinda Ardern announced that she’s planning a summit in Paris alongside French President Emmanuel Macron. The summit’s goal is to have industry and world leaders agree to a pledge called the “Christchurch Call” to eliminate terrorist and violent extremist content online. In the announcement, Ardern said: “The March 15 terrorist attacks saw social media used in an unprecedented way as a tool to promote an act of terrorism and hate. We are asking for a show of leadership to ensure social media cannot be used again the way it was in the March 15 terrorist attack…We all need to act, and that includes social media providers taking...