After President Trumpand at Tuesday's presidential debate, the group added the phrase to its online logo. Law enforcement and former group members say the president's comments will embolden many factions of the group that hold extreme racist views.
In recent months, Proud Boys have patrolled streets and held demonstrations to counter what they claim is violence from anti-fascist extremists. But their presence has provoked violence in cities like Portland and Kalamazoo, Michigan.
The group was founded in 2016 by Vice Media co-founder and self-described provocateur Gavin McInnes, who has often preached language condoning violence.
"You have to be a western chauvinist," he said, explaining the origins of the group. "We beat the crap out of them ... We're not going to pick fights, but if they pick fights with us, we're going to finish them."
Former members say its nationalist message has provided cover for white supremacism.
"It evolved into this other thing," said comedian Dante Nero, who was an early member of the group. "It started to grow ... I went on the Facebook page and there was all this racist stuff on the Facebook page."
The Proud Boys deny that they are a white supremacist group.
"There's not too many racists and white supremacists that actually admit to being white supremacists," Nero told CBS news correspondent Jeff Pegues.
Asked if he thinks Mr. Trump is "speaking their language," Nero said, "Absolutely. It's on their website. They're emboldened by it."
"They feel like they are the guardians to make America great again," he added.
According to the FBI, violence from white supremacist groups is the single biggest threat to national security, as the president's own FBI director testified last month.
"Racially motivated violent extremists over recent years have been responsible for the most lethal activity in the U.S.," director Christopher Wray said.
And with racial tension increasing across the country, the escalating rhetoric poses a challenge for police departments nationwide.
"When you hear the president of the United States saying things like that they should ... stand by, that type of signaling to be ready for violent clashes does nothing but empower hate groups," said Charlottesville Police Chief Dr. Rashall Brackney.
In a statement to CBS News, a representative of the Proud Boys said in part, "We condemn all forms of -isms, whether it be racism, fascism, communism, or socialism."