Harold Edmund Netkin, 69, was initially handcuffed Wednesday night, but was later released without being cited, said Garden Grove Police Lt. Mike Handfield.
Netkin's car was surrounded as he arrived at the Garden Grove Women's Club, 9501 Chapman Ave., and demonstrators rocked the vehicle and banged on it, Handfield said.
"We determined it was reasonable for him to move forward," Handfield said.
Two people who were standing in front of Netkin's car fell down when he moved forward, the sergeant said. One complained of knee and shoulder pain and was taken to a local hospital, he said.
According to broadcast reports, the other also went to the hospital.
Police were aware of the demonstration and had five dozen officers on scene "expecting to keep the peace," Handfield said. But some of the estimated 300 demonstrators were there "not to protest but to commit criminal acts," he said.
"A small contingent of people that were troublemakers had backpacks filled with full cans of soda that they were throwing and also cans filled with marbles that they threw," Handfield said.
Some of the protesters wore rubber gloves and donned sweatshirt hoods pulled tightly so only a small portion of their faces could be seen, he said.
Those arrested were identified by police as Hugo Sarmiento Vanlid, 24, Ivan Obed Silva, 26, Shane William Sparks, 21, Fernando Chirino, 23, and Kurt Takeshi Isobe, 18.
Their cities of residence were not immediately available.
"The case will go to the district attorney, who will have the opportunity to look at all the facts we did," Handfield said.
Prosecutors will look at the actions of both Netkin and the arrested protesters, he added.
About 300 people were outside the club as Minuteman Project founder James W. Gilchrist talked to about the same number of people inside, attendees said.
Handfield said some protesters went inside the meeting and appeared to be using cell phones to communicate with those outside.
"It got out of control in terms of protesters getting violent," he said.
Jan Tucker, chair of the California Association of Licensed Investigators, said he accompanied state and local leaders of the League of United Latin American Citizens to the talk.
He said the atmosphere inside the meeting "was the flip side" of what was happening outside.
"It was extremist inside," Tucker said. "The audience was so hostile inside we were afraid to ask questions."
Attendees who were not members of the club were charged $5 and reportedly had to write down their names, addresses and telephone numbers to get inside.
Tucker said he was not disruptive, but was still asked to leave. After refusing, an officer came over and spoke to him, but Tucker said he still plans to sue the California Coalition for Immigration Reform for allegedly violating his rights "because they tried to get me arrested."
Gilchrist spoke for about 90 minutes, blaming high housing costs and low wages on illegal immigration. He was presented with a cake for his earlier border monitoring, Tucker said.
Tucker said members of LULAC were outside demonstrating, but were strictly cautioned to remain non-violent and to refrain from provoking police.
Tucker said none of the people he spoke to after the event mentioned that Netkin's van was surrounded or was being hit, but insisted that he gunned the car at people.
Handfield said protesters broke a car window of "some innocent person coming to listen" to the talk. Police did not witness the vandalism, and no arrest was made.
At about 10 p.m., officers declared an illegal assembly, ordering the crowd to disperse.
The group, which recently patrolled a portion of the U.S.-Mexico border in Arizona, has announced plans to patrol a portion of the border in California on Aug. 1.
The Minuteman Project has been accused of racism. Gilchrist has denied the charge, saying his group merely wants to stop illegal immigration.
The group has drawn praise from Gov. Arnold Schwarzenegger, but its members were referred to as vigilantes by President George W. Bush.
Video: Minuteman Protest
Images: Minuteman Protest