Under federal law, a riot is a public disturbance involving an act of violence by one or more persons assembled in a group of at least three people. Inciting a riot applies to a person who organizes, encourages, or participates in a riot. It can apply to one who urges or instigates others to riot. According to 18 USCS § 2102 "to incite a riot", or "to organize, promote, encourage, participate in, or carry on a riot", includes, but is not limited to, urging or instigating other persons to riot, but shall not be deemed to mean the mere oral or written (1) advocacy of ideas or (2) expression of belief, not involving advocacy of any act or acts of violence or assertion of the rightness of, or the right to commit, any such act or acts.”

You'd think a law enforcement officer charged with keeping the peace would be familiar with 18 USCS § 2102.