Speaking at Frank Ogawa Plaza in front of City Hall, where tents have again sprung up, Moore said people throughout the US were "disgusted" and "horrified" when police fired tear gas and bean bags and took other aggressive actions against protesters Tuesday night.
Although police cleared protesters and their tents from the plaza Tuesday morning, the protesters and their tents returned the next day.
Wearing blue shorts, a blue hooded sweatshirt and a gray hat, Moore told the crowd, "Millions have seen this and are inspired by you because you came back the next night."
He said, "This week in Oakland, California, will go down as a watershed moment" in the "Occupy Wall Street" movement.
Moore said the protest is growing quickly across the country, saying, "I've never seen a movement take form so fast."
Moore rhetorically asked the crowd, "There's no turning back, is there?" and the crowd answered with a loud "No!"
He said the movement has already had "a number of victories in our first six weeks," saying, "We've killed despair across the country and we've killed apathy."
Moore, who has visited many "Occupy Wall Street" protests across the US, said the national discussion six weeks ago was the debt ceiling and the deficit but "this movement shut down that discussion," using a profanity to describe talk about those subjects.
Among the protesters who were injured Tuesday night was Iraq War veteran Scott Olsen, a 24-year-old Daly City man, whom his friends said was critically injured when he was hit in the head with a projectile fired by police.
Moore asked for a moment of silence for Olsen "in his honor and in hope that he will recover quickly from his injuries."
Moore said, "It's absolutely criminal that this young man went to Iraq for a war he didn't agree with and the only place he had to worry about was here in his own country, in Oakland, California."
Moore said he hopes he can talk to Oakland Mayor Jean Quan to ask why police responded so aggressively to protesters but he hasn't yet heard from her.
At least three Oakland City Council members were among the crowd listening to Moore: Rebecca Kaplan, Jane Brunner and Desley Brooks.
