Here’s the definition of California penal code sec. 415
aka disturbing the peace.
415. Any of the following persons shall be punished by imprisonment
in the county jail for a period of not more than 90 days, a fine of
not more than four hundred dollars ($400), or both such imprisonment
and fine:
(1) Any person who unlawfully fights in a public place or
challenges another person in a public place to fight.
(2) Any person who maliciously and willfully disturbs another
person by loud and unreasonable noise.
(3) Any person who uses offensive words in a public place which
are inherently likely to provoke an immediate violent reaction.
Giving the finger may be interpreted by some to be protected speech when the act is directed to a public official, but I don’t think the same applies when directed to a private person.
In other words, certain actions or words inherently likely to provoke a violent reaction still constitute a breach of the public peace.
I think it can easily be shown that not only was the finger being given by the protester to everyone in the vicinity, but also that his actions were accompanied by inflammatory words as well.
Just because the law has been selectively enforced doesn’t negate the fact that it’s still a law on the books.
While giving a finger MIGHT be breach of peace, sucker punching someone is clearly assault and battery.