Domestic terrorist attacks motivated by white nationalist ideology make up a growing portion of cases the FBI is investigating.

But the FBI has had trouble "identifying and disrupting" the threat in part because of "the ease of online self-radicalization to violence," Michael McGarrity, the assistant director of the FBI's counterterrorism division, told the House Homeland Security Committee in May.

The FBI has also pushed back on calls to investigate racist and threatening messages posted to social media out of fear that it could violate individuals' First Amendment rights.

But "it's clear that many of the people targeted for investigation for allegedly supporting the Islamic State were initially identified because of something they said online," one former FBI agent told The New York Times.

A former FBI official told The Washington Post that President Donald Trump's attacks against the FBI have led to "reluctance among agents to bring forth an investigation that targets what the president perceives as his base."

Another former senior FBI official echoed that view, telling INSIDER, "Now agents are scared of doing their jobs — afraid to do the one thing they're tasked with, which is to keep Americans safe — because they're so wary of pissing off the guy in the Oval Office."

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Just two weeks ago, FBI director Christopher Wray was harshly criticized during a hearing before the Senate Judiciary Committee for the bureau's focus — or lack thereof — on white supremacist violence.

"The term 'white supremacist, ' 'white nationalist,' is not included in your statement to the committee when you talk about threats to America," Democratic Sen. Dick Durbin of Illinois told Wray. "There is a reference to racism, which I think probably was meant to include that, but nothing more specific."

Wray responded that the FBI stopped using separate categories for white supremacists and "black identity extremists," but he added, "I will say that a majority of the domestic terrorism cases that we've investigated are motivated by some version of what you might call white supremacist violence."

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FBI Director Christopher Wray. FBI.gov

This week, the FBI came under sharp scrutiny over how it addresses domestic terrorism inspired by white nationalism in the wake of two mass shootings over the weekend in El Paso, Texas, and Dayton, Ohio.

The FBI currently has 850 open domestic terrorism investigations. Of that number, 40% involve racially motivated violent extremism, and a majority of those cases involve white nationalists, the bureau said.

"We will bring the full resources of the FBI to bear in the pursuit of justice for the victims of these crimes," Wray said in a statement Sunday night.

But despite Wray's assurance and increased public focus on the danger of white nationalism, the FBI is still somewhat hamstrung in how it responds to the threat.

In particular, current and former officials have pointed to two factors that they believe preclude the FBI from effectively combating white supremacist violence: the rapid growth of social media and its implications for free speech, and President Donald Trump's polarization of the political climate and his attacks against the law enforcement and intelligence community.

Read more: 'We are not helpless here': Former President Barack Obama made a rare public statement calling for action on gun violence after mass shootings in El Paso and Dayton

The FBI isn't equipped to monitor the 'millions' of racists, anti-Semites, homophobes, Islamophobes, and xenophobes online

Michael McGarrity, the assistant director of the FBI's counterterrorism division, highlighted a few reasons why the bureau has faced hurdles when confronting homegrown violent extremism.

The FBI has had trouble "identifying and disrupting" the threat in part because of "the ease of online self-radicalization to violence," McGarrity told the House Homeland Security Committee in May.

"We are most concerned about lone offenders, primarily using firearms, as these lone offenders represent the dominant trend for lethal domestic terrorists," McGarrity added. "Frequently, these individuals act without a clear group affiliation or guidance, making them challenging to identify, investigate, and disrupt."

He said the FBI anticipates that racial minorities, the US government, and law enforcement will continue to be "significant targets" for domestic terrorists.

The exponential growth of social media also poses a new and often unfamiliar challenge to law enforcement authorities. The FBI is under mounting pressure to address racist and threatening messages posted to social media. The bureau said in a statement to The New York Times that it "does not and cannot police ideologies under the First Amendment."

A vigil for the El Paso shooting victims. Associated Press

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But Michael German, a fellow at the Brennan Center for Justice at the NYU School of Law and a former FBI agent, told The Times that based on prosecutions, "it's clear that many of the people targeted for investigation for allegedly supporting the Islamic State were initially identified because of something they said online."

German added, however, that the overwhelming presence of white-supremacist content online poses a unique problem.

"There are relatively few Americans voicing their support for ISIS online," he said. "But there are millions of racists, anti-Semites, Islamophobes, homophobes, and xenophobes who engage in eliminationist rhetoric about the communities of people they fear and hate every day on social media and radio talk shows. Even if the FBI wanted to monitor this hate speech, they wouldn't have the resources, or any way to distinguish between those who talk and those who act."

White nationalists and Trump's 'base'

US President Donald Trump speaks at a "Make America Great Again" rally at Minges Coliseum in Greenville, North Carolina, on July 17, 2019. NICHOLAS KAMM/AFP/Getty Images

Other officials say President Donald Trump's own words and actions may not only be the inspiration for homegrown violent extremists, but they could also contribute to a lack of willingness by law enforcement to prosecute such cases.

"There's some reluctance among agents to bring forth an investigation that targets what the president perceives as his base," Dave Gomez, a former FBI supervisor who oversaw terrorism cases, told The Post. He also said the hesitation stems largely from Trump's public criticism of the FBI, particularly as it investigated Russia's interference in the 2016 US election and whether members of the Trump campaign conspired with Moscow.

One former FBI official who retired last year echoed that view and told INSIDER, "This is what national security officials have been warning about since the president started spewing vitriol at the law enforcement community, despite running a campaign calling for law and order."

"Now agents are scared of doing their jobs — afraid to do the one thing they're tasked with, which is to keep Americans safe — because they're so wary of pissing off the guy in the Oval Office," the former official added.

Trump's steady push to fill the Justice Department, which oversees the FBI, with loyalists like Attorney General William Barr may also be a factor.

Gomez told The Post he doesn't think "there's any faith by the FBI right now that the Justice Department is an independent law enforcement organization. I think the FBI is up to the challenge of investigating white nationalism and white supremacy as a domestic terrorism threat, they just have to be allowed to do it."