Have you considered that the increasing activity of these groups is an actual indicator of increasing radical rightism in the U.S., and not a completely unrelated coincidence used by those violent leftists to spread their shrill propaganda?
These people are coming in to attempt to intimidate those they see as lesser. This is why they come to the most left-leaning cities in the nation - Charlottesville, Richmond, Boston, and now DC - because they all dream of being 'based stick man' and seeing their political opponents fear them. This is provocation, and cannot be ignored by the residents who just want to live in peace. Where those flags go unopposed, burning crosses are not far behind. You can continue to see this as baseless hyperbole if you want, until these people show up at your front door.