Nobody meant for this to happen. Facebook didn't mean to facilitate a genocide. Twitter didn't want to be used to harass women. YouTube never planned to radicalise young men. But with billions of users, every time these platforms tweak their algorithms to generate more 'engagement', they bring unrest to previously settled communities and erode our relationships. After all, anger keeps you engaged. It has been hard to address climate change precisely because it has been happening slowly and in plain sight. In the same way, we urgently need to address this social crisis before we reach an irreversible tipping point.