The U.S. Supreme Court famously held that “freedoms of speech and press do not permit a State to forbid advocacy of the use of force or of law violation except where such advocacy is directed to inciting or producing imminent lawless action and is likely to incite or produce such action.” 

Speaking in the context of speech having the tendency to incite violence, the European Court of Human Rights declared that “there is little scope… for restrictions on political speech or on debate on questions of public interest”, including the “divisive ones”.