TAMPA, Fla. (AP) — A white man charged with cyberstalking and making racist threats against a black activist in Virginia was ordered Monday to remain in custody, in a case that could test the boundaries of when online trolling becomes a criminal threat.

U.S. Magistrate Judge Thomas Wilson ordered Daniel McMahon to continue to be jailed, saying his mental instability, ability to obtain firearms and praise of mass shootings in Pittsburgh and Charleston, South Carolina, through his online communications raise concerns he poses a threat to the community.

"He is cheering on mass shooters. That is what really bothers me," Wilson said of the 31-year-old Brandon, Florida, man. "This is a red flag."

McMahon's defense attorney asked the magistrate to let him be released into the custody of his father on $50,000 bond. Attorney Nicholas Matassini argued that McMahon's diatribes were only political speech.

"It's protected by the law. I don't think it exhibits any manifest danger to the community," Matassini said.

A few minutes later, Assistant U.S. Attorney Carlton Gammons told the judge it wasn't free speech.

"Any threat of violence against another person is not free speech," Gammons said. "You can't do that."

An indictment unsealed last week in Virginia said McMahon expressed white supremacist views on his social media accounts. It said McMahon used his social media accounts to intimidate the activist, Don Gathers, and interfere with his campaign to run for a seat on the Charlottesville, Virginia, city council.

During Monday's hearing, the prosecutor presented as evidence some of the comments McMahon had made on social media, including ones repeating that Gathers needed to be stopped through "a diversity of tactics." Gammons said that term meant physical violence.

McMahon's mother told detectives that her son didn't like African Americans, Jews or gay people and that she worried her son exhibited some of the characteristics of mass shooters, said Siobhan Maseda, a detective for the Pasco County Sheriff's Office, who assisted in McMahon's arrest.

Former Justice Department attorney Justin Levitt, a law professor at Loyola Law School in Los Angeles, said he doesn't know of any other recent cases in which someone has been charged with the federal crime of interfering with a candidate for elective office. The Justice Department doesn't prosecute internet trolls for spewing hateful messages; the conduct must rise to the level of an actual threat of violence or something similarly serious, Levitt said.

"There can be some dispute about what that actually entails on the margins. That's why you don't see these kinds of cases very often," said Levitt, who served as a deputy assistant attorney general in the Justice Department's civil rights division from September 2015 to January 2017. Levitt isn't involved in McMahon's case.

A hateful social media message led to a federal criminal charge in another recent case. A North Carolina man, Joseph Cecil Vandevere, was charged in June with anonymously threatening to lynch a Muslim-American man campaigning for a state Senate seat in Virginia. Vandevere was indicted on one of the same charges that McMahon faces: making interstate threats. The case is still pending.

Others have accused McMahon of bombarding them with hateful, threatening messages through online aliases.

Lindsay Ayling, a graduate student at the University of North Carolina-Chapel Hill, said McMahon has used an account on Gab under the pseudonym "Jack Corbin" and anonymous accounts on other social media platforms to repeatedly harass her over the past year. The messages included sexually violent threats and a post mocking her brother's death.

Ayling, 31, said the harassment began after she became an outspoken advocate for taking down Silent Sam, a Confederate statue that protesters toppled last year on the university's campus.

"I have been pretty stressed out," she said. "I don't know if I can articulate the toll the harassment has taken."

Ayling said she refuses to back down and retreat from the wave of online hate that McMahon and his followers have unleashed.

"Ultimately, it's not my fault if Nazis choose to harass me. It's their fault," she said.

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Kunzelman reported from College Park, Maryland.