Proud Boys leader Enrique Tarrio was sentenced to more than five months in jail for burning a church's Black Lives Matter banner in December.
The incident happened just days before the January 6th Capitol Hill riots.
"This court must respect the right of any citizen to peacefully assemble, protest, and make his or her views known on issues," the judge said during sentencing, according to CNN. "But Mr. Tarrio's conduct in these criminal cases vindicate none of these democratic values. Instead, Mr. Tarrio's actions betrayed them."
He also pleaded guilty to attempting to possess a high-capacity gun magazine and later apologized, saying he made a "grave mistake."
"What I did was wrong," Tarrio said during a videoconference, as the Associated Press reports.
"His careless act of violence and hatred, targeted at a congregation of individuals with a lived history of social and racial injustice, had the presumably desired effect," Rev. Dr. Ianther Mills, senior pastor of the church, said. "Asbury was forced to reckon with the very tangible evidence that we continue to live in a world where people radicalize hate based upon race and skin color."