"Activities that . . . involve acts dangerous to human life and are in violation of the criminal laws of the US or any state and "appear intended: to intimidate . . a civilian population."
See 18 USC 2331(5).
He incites violence in violation of federal & state law via @Twitter that IMO is complicit. Violence is directed at persons of color that "appears intended to intimidate" them constituting a "civilian population" under the statute.