At a news conference on Sept. 28, Mr. Long said he was protecting an older white man when he lit the spray can.
“I was not in the wrong,” Mr. Long said. “A guy threw a spray can at me, and I took it to my advantage.”
The rally attracted hundreds of white nationalists to Charlottesville, where they protested the removal of a statue of Robert E. Lee. Violent scuffles erupted throughout the weekend, and a 32-year-old woman, Heather D. Heyer, was killed when a man drove into a crowd of counterprotesters. James Alex Fields Jr., who is suspected of driving the car, was charged with second-degree murder.
The organizer of the rally, Jason Kessler, complained on Twitter that the charges Mr. Long faced were inadequate. He wrote: “Try ‘No mask law,’ ‘Brandishing a firearm,’ ‘burning an object with intent to intimidate.’ Disorderly conduct for using a flamethrower?”
Under Virginia code, the charges Mr. Long face are Class 1 misdemeanors punishable by up to a year in jail.
According to one warrant, the assault charge was based on an allegation from Harold Crews, a self-described Southern nationalist and the state chairman of the North Carolina League of the South. Neither Mr. Crews nor the arresting officer, Will Cole, could be reached for comment.
A criminal defense lawyer in Charlottesville, J. Lloyd Snook III, disagreed with Mr. Kessler’s assessment, particularly about the appropriateness of mask and burning-object charges, both of which are felonies.
“The commonwealth attorney seems to be reserving felonies for situations when people got hurt, and when Corey Long fired off the spray can, nobody got hurt,” he said.
Mimi Arbeit, an organizer with Indivisible Charlottesville, said the city should drop the charges. In an email, she said Mr. Long “was among the Charlottesville community members who showed up to confront white supremacist fascism.”
Within minutes of his release on Friday, Mr. Long returned to protesting.
After three Unite the Right activists — Nathan Damigo, Evan McLaren and JonPaul Struys — were convicted in Charlottesville General District Court of misdemeanor charges of failing to disperse, Mr. Long pumped a fist in the air, shouted “black power,” and joined four others in following the three men into a parking garage while shouting them down with denunciations of white supremacy.
This was inside the same parking garage where DeAndre Harris, a 20-year-old black man, was beaten by a group of white nationalists on the day of the rally. Mr. Harris was assaulted just a few moments after he had intervened in a scuffle that broke out and Mr. Long, his friend, had tried to yank away a Confederate flag from a marcher.
Last week, the police arrested a third man in connection with the beating of Mr. Harris. In what became one of the rally’s most prominent acts of violence after videos of the attack spread on social media, six men surrounded Mr. Harris and beat him with a metal pipe and wooden boards. He sustained a broken wrist and a head wound that required 10 staples.
Mr. Harris was arrested the day before Mr. Long was arrested, also based on a charge from Mr. Crews.
Mr. Long claimed on Friday that his arrest was retaliation and that the police were “in the pocket” of white supremacists. Chief Al S. Thomas Jr. of the Charlottesville Police Department said in an interview on Friday he would address such allegations “at the appropriate time.”