Greenwood said he made a decision to let the black-clad protesters demonstrate in the park because there was "no need for a confrontation over a grass patch".
Gibson abruptly canceled the San Francisco rally, originally permitted to be held at Crissy Field near the Golden Gate Bridge.
RT's Ruptly agency's feed from the scene was abruptly cut off after masked protesters, purportedly members of Antifa, approached the camera and demanded the crew "move that thing".
Protesters said they feared the violence would create a much-needed distraction for Trump and his supporters need to deflect attention from his response to Charlottesville.
San Francisco Police Chief Bill Scott said there was one arrest Saturday for public intoxication.
He was among half a dozen speakers who initially planned to speak at the rally.
Shortly after arriving at the Berkeley rally, the prominent right-wing organizer was met with resistance from members of Antifa, an anti-fascist movement.
The San Francisco Police Department, however, did advise on its official Twitter account for people to stay away from the area. "We have a chant, we want peace in our parks, no to Nazis, yes to Marx!" says Isabel White, a spokeswoman for Groucho Marxists Against Hate and White Supremacy. At the same time, a strong contingent of riot-ready police officers from Berkeley and other local agencies set up lines to keep the two sides from fighting. No further details were provided. Any group that claims "hate speech is not free speech" is going to become not just censorious but violent pretty quickly. Gibson was one of the people assaulted by the group.
In the days leading up to the planned events Cummings and Gibson, who is Japanese-American, consistently denounced racism. He also said Saturday in a Facebook post that he would pop up at random sites throughout the city to speak with residents.
At Alamo Square Park and elsewhere in the city, counterprotesters, who had shown out in large numbers, rallied and rejoiced.
People were stopped from entering the park. But officers had fenced off the park by early Saturday morning. (Sheraz Sadiq/KQED) Ben Stern, a 95-year-old survivor of the Holocaust (center, in cap and blue shirt), leads a march of Jewish activists in Berkeley to protest against far-right activities in that city. Demonstrators flooded the streets even though the rally had been canceled. Another right-wing rally titled "Patriot Prayer" also was canceled, reported KCRA.