As he addressed reporters, several hundred protesters and a much smaller number of counter-demonstrators gathered in the streets outside.
The longtime Maricopa County sheriff was the star attraction for a sold-out event that concerned some Republicans, who worry about the party's ability to appeal to Latinos.
Arpaio was convicted for actions related to alleged racial profiling of Latinos and then pardoned by Trump. That was one issue Arpaio took on.
"I end up on the defense table for a trial on a contempt of court, where everyone's bragging about the criminal sheriff," he said.
"One day they're going to find out the real story about this," he said. "I'm not guilty. I got two parking tickets in my life -- two. I'm 85 years old and I end up charged of contempt of court because one judge hates me."
He also said he would support Trump "to the end."
"He spoke out about illegal immigration. All these people running for office didn't even want to talk about it. They wanted it to go away," Arpaio said. "At least he brought it out, forcing everybody else to talk about it."
But he took a more nuanced position than Trump on professional football players who protest peacefully during the pregame national anthem. Trump wants those players blackballed from football, and urged fans to exert pressure by boycotting the sport.
"I still get a chill every time I hear the national anthem," Arpaio said. "The flag is still something to me, and I'm sure many Americans feel the same way. But everybody has the 1st Amendment right to voice their opinion — not that we all have to agree with it."
The fundraiser was billed as an event to proclaim a defense of the 1st Amendment — free speech — and the 2nd Amendment — which includes a right to bear arms. Tickets ranged from $60 to $200 apiece, with the latter including a photo with the guest of honor.
"Join us to stand up to the threats against our First Amendment freedom of speech rights!" the event handbill proclaimed. "The left tries to shout us down and make us cower, but we will not give in to their bullying or fear tactics."
Outside, police cordoned off the entire block on both sides of the speaking venue, a banquet hall. Demonstrators gathered on opposite sides of the street beyond the barriers.
Fresno Police Chief Jerry Dyer said the protesters were largely cooperative and he appeared anxious to avoid making arrests. He became especially concerned when anti-Arpaio demonstrators crossed the street and began to mingle with the opposing side. He urged people who disagreed with one another to maintain a respectful and safe distance.
"Please give yourself some space right now," Dyer called out through a bullhorn. "I'm asking both sides."
He also stepped in personally, positioning himself as a barrier between agitated people, as did his officers.
Before the event, local Republican leaders defended their invitation to Arpaio.
"People all around America respect Sheriff Joe," said Fred Vanderhoof, a retired teacher and party chairman. "They realize he's being attacked by the left."
But other Republicans see a damaging message for a party struggling for relevance in an increasingly Democratic state. And especially to the group that is now the largest in California: Latinos.
Arpaio was convicted in July of criminal contempt for violating a federal court order to stop racially profiling Latinos in Arizona. He was scheduled to be sentenced Oct. 5 and faced a maximum of six months in jail. President Trump pardoned him in August.
"It's an unmitigated disaster," said Mike Madrid, a Republican political consultant who has worked for more than two decades to garner the Latino vote for the GOP, primarily in California. "It's beyond belief that a man convicted of racial profiling is held up as an iconic figure in the party of Ronald Reagan and Abraham Lincoln."
Madrid said the Fresno County GOP's praise of Arpaio, coupled with Trump's election, have set back their efforts with Latinos — the fastest-growing segment of the electorate — for at least a generation.
Dyer estimated that the anti-Arpaio group outnumbered the supporters 10 to 1. Some Arpaio supporters left their demonstration to attend a VIP reception in hopes of meeting him.
The anti-Arpaio group held up signs with messages such as: "Shame" and "Guilty." One man held aloft a sign that read: "Mexican Americans served with honor. Racist Republicans have none."
Other messages expanded on politically compatible themes: "Impeach Trump Now" and "Smash White Supremacy."
On the other side, people hoisted American flags as they converged on a patch of grass. "Trump, America, Arpaio," one man shouted.
Some Republican politicians, including Fresno Mayor Lee Brand, skipped the event.
"I will be out of town, but I wouldn't go even if I was there," Brand said in a prepared statement. "While popular with some, Arpaio is a villain to others. My job as mayor is to unite the community and I am focusing my time and energy on events and policies that further those goals."
"We want to stand up for freedom of speech," said Vanderhoof, the local party chairman. "We have a right to invite anyone we want and he has a right to speak."
Vanderhoof said he did not believe that inviting the controversial former sheriff would hurt with Latino voter outreach efforts.
On Friday morning, Democratic National Committee leader Tom Perez blasted the choice of Arpaio as a speaker.
"It is an abomination that the Fresno County Republican Party has decided to go through with a fundraising event featuring Joe Arpaio, one of our nation's most notorious agents of racism and bigotry," he said in a statement.
Arpaio, who once labeled himself as "America's toughest sheriff," became a polarizing figure for the Latino community in Arizona and throughout the country after thrusting himself into the national spotlight for his aggressive tactics against immigrants in the country illegally.
In some ways, Arpaio's brash rhetoric against illegal immigration rhetoric made him a precursor to Trump's successful campaign for the presidency. Both had also pushed the "birther" conspiracy that President Obama was born in Africa and was not a legitimate president.
Kevin Spillane, a Republican political consultant who has concentrated on Latino inclusion for the least 20 years, called the Fresno GOP's move "tone deaf," contending that most of them are volunteer activists who don't know the full story about Arpaio's tenure in Maricopa County.
But Spillane said he did not believe that having Arpaio speak would be as detrimental to the party's efforts to expand its base to Latinos as others thought. He said the GOP has made gains in getting Latino Republicans elected to state and local offices, including school boards and city councils.
"They are the future of the Republican Party, if there is going to be a future," Spillane said. "Arpaio belongs to the past, and it's unfortunate that Fresno County Republicans did not decide to side with the future and decided to side with the past."
8:45 p.m.: This article was updated with photos from Friday's event.
8 p.m.: This article was updated to include Arpaio's comments and more details about the police handling of demonstrations.
6:45 p.m.: This article was updated with comments from the Fresno police chief.
5:35 p.m.: This article was updated with comments from protesters.