I'm just going to agree to disagree with you on this one rather than taking over the thread like last time haha.
Well, riddle me this. Under California Penal Code (I'll post the sections at the bottom), everyone still there, be them protestors or people simply watching, were equally guilty of an unlawful assembly. They attempted to take people who were arrested by force (preventing the officers from leaving), which is by definition a lynching. As such, they were, by definition, commiting a riot. Why wasn't everyone in that circle arrested and charged with rioting? If the police truly felt like they were threatened, why not hit the protestors up with the much more serious charges?
404. (a) Any use of force or violence, disturbing the public peace, or any threat to use force or violence, if accompanied by immediate power of execution, by two or more persons acting together, and without authority of law, is a riot.
404.6. (a) Every person who with the intent to cause a riot does an act or engages in conduct that urges a riot, or urges others to commit acts of force or violence, or the burning or destroying of property, and at a time and place and under circumstances that produce a clear and present and immediate danger of acts of force or violence or the burning or destroying of property, is guilty of incitement to riot.
405a. The taking by means of a riot of any person from the lawful custody of any peace officer is a lynching.
407. Whenever two or more persons assemble together to do an unlawful act, or do a lawful act in a violent, boisterous, or tumultuous manner, such assembly is an unlawful assembly.
408. Every person who participates in any rout or unlawful assembly is guilty of a misdemeanor.
409. Every person remaining present at the place of any riot, rout, or unlawful assembly, after the same has been lawfully warned to disperse, except public officers and persons assisting them in attempting to disperse the same, is guilty of a misdemeanor.
Source:
http://www.leginfo.ca.gov/cgi-bin/displaycode?section=pen&group=00001-01000&file=403-420.1