Digital rights and free speech advocates are up in arms over Tuesday's announcement of an agreement between the European Commission and four leading U.S. social media firms -- Facebook, YouTube, Twitter and Microsoft -- on a Code of Conduct designed to crack down on hate speech. The companies have agreed to adopt a system that allows users to flag illegal hate speech and incitement to violence. They also agreed to review flagged posts within 24 hours and to take appropriate action, such as removing them or blocking access.