New York Gov. Andrew Cuomo has called for a federal and state investigation into a fight last week at a Republican Party event in Manhattan between members of the Proud Boys, a far-right men's organization, and protesters from the anti-fascist group Antifa.

One video clip from the altercation posted online appears to show a member of the Proud Boys kicking an Antifa protester while yelling “faggot.” (It can be heard in the video below at approximately 45 seconds.)

Here's video of the Proud Boy mob assault from tonight up close pic.twitter.com/frW09dcDHn — Adam (@leftkist) October 13, 2018

But experts say that proving that a hate crime had been committed, even with evidence of a gay slur being used, would be difficult, given other circumstances surrounding the Oct. 12 incident at the Metropolitan Republican Club in Manhattan.

The key would be proving that there was intent to target a victim because of actual or perceived membership in a protected class, like sex, sexual orientation, race or gender identity.

Hate crimes are defined differently by federal and state statutes, according to experts interviewed by NBC News. And while the Proud Boys are well-known for their anti-Muslim and anti-feminist ideology, they are unique among far-right groups in that they explicitly welcome gay men. On the other hand, the group and their founder have used their platform to broadcast transphobia to an audience of millions.

“You can anticipate all kinds of circumstances where people in different groups get in arguments, and because of whatever reason it escalates to name calling, said Frank Pezzella, a criminology professor at John Jay College of Criminal Justice and an expert on hate crimes. “But that isn't necessarily the kind of bias incident we are talking about.”

FBI assistance can be requested by states looking into alleged hate crimes, which is what Cuomo did on Sunday, and Pezzella said in these cases the bureau looks for 14 bias indicators. (Cuomo also asked the state police's hate crimes unit to investigate.)

“Words are one,” Pezzella said, and in this case, that indicator is there. Others include attacks on religious holidays or attacks following events held by groups known for hate ideology.

Other charges the Proud Boys could be charged with, Pezzella said, include gang violence or terroristic threats. “But unless a prosecutor can be sure he is going to be able to prove bias motivation — these guys may be prosecuted, but it won’t be under hate crimes statutes,” he added.

Richard Saenz, a senior attorney at Lambda Legal, an LGBTQ civil rights and legal organization, said the use of a gay slur alone would likely not be enough to deem the altercation a bias incident.

“What you have to do is show they willfully want to cause harm because of your religion, gender identity or sexual orientation,” Saenz said. Even with the tape showing a Proud Boy using a slur, “the burden would still be on the prosecutor to establish the intent required by the statute.”

The clearest difference between the Proud Boys and the Antifa protesters — political ideology — is not protected by either state or federal hate crimes statutes. So whichever group started the fight, if it was over their political ideology, existing laws do not categorize these types of attacks as hate crimes.

One issue is that the Proud Boys explicitly endorse and embrace the exact type of violence caught on tape last weekend: violence against political opponents.

The Proud Boys, which has been deemed a “hate group” by the Southern Poverty Law Center, was founded by Vice Magazine co-founder Gavin McInnes in 2016. To become a “first-degree” member of the group, a man must utter the phrase “I am a Western chauvinist and I refuse to apologize for creating the modern world.” To become a “second-degree” member, he must survive a beating by other Proud Boys while reciting the names of breakfast cereals. “Third-degree” members must get a Proud Boys tattoo, and “fourth-degree” members have to engage in a fight with left-wing protesters, which is exactly what happened in New York. The group’s own rules define a reward for the assault captured on tape last weekend.

Anti-fascist protesters often meet McInnes at his public appearances, like they did last week at the Metropolitan Republican Club, and there have been many clashes between his supporters and left-wing protesters.

McInnes appeared on the conservative cable news network Newsmax after the fight to tell his side of the story. During the interview, he attempted to explain why a so-called Proud Boy would use the word “faggot” during the attack.

“It’s a terrible word to use, but you know when someone’s adrenaline is pumping, he’s going to say, ‘Are you brave now, f-word?’ He didn’t mean it like it was some sort of homosexual attack,” McInnes said.

McInnes’ controversial writings and commentary have gotten him fired from an ad agency he founded himself and — just this year — removed from Twitter.

The Metropolitan Republican Club of New York defended their decision to invite McInnes to speak, saying in a statement they are “staunch supporters of the 1st amendment.”

The club denied any knowledge of the altercations that took place near the club and contended that McInnes’ speech was “certainly not inciting violence.” However, according to McInnes’ own account of the event on Newsmax, he used a plastic sword to simulate the 1960 assassination of Japanese socialist Inejiro Asanuma by a far-right extremist.

Neither the FBI nor the New York State Police Hate Crimes Unit immediately responded to requests for comment about any potential investigation.

According to the most recent FBI hate crimes data, 17 percent of hate crime victims in the U.S. in 2016 were targeted because of their sexual orientation, and most of those victims were gay men.

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