“It is one of the most hallowed precepts in modern constitutional law: Freedom of speech may not be curbed unless it poses a ‘clear and present danger’ — an actual, imminent threat, not the mere advocacy of harmful acts or ideas. But in response to the Islamic State’s success in grooming jihadists over the Internet, some legal scholars are asking whether it is time to reconsider that constitutional line.”
Source: ISIS Influence on Web Prompts Second Thoughts on First Amendment – The New York Times