“Strong and effective extemporaneous rhetoric cannot be nicely channeled in purely dulcet phrases. An advocate must be free to stimulate his audience with spontaneous and emotional appeals for unity and action in a common cause. When such appeals do not incite lawless action, they must be regarded as protected speech. To rule otherwise would ignore the profound national commitment that debate on public issues should be uninhibited, robust, and wide-open.” – National Ass’n for the Advancement of Colored People v. Claiborne Hardware Co., 458 U.S. 886 (1982) (internal cites and quotation marks omitted)