Anarchists clashed with riot police in the streets of Washington, D.C., during their anti-fascist protest to mark Donald Trump’s presidential inauguration. Blockades of dozens of helmeted police advanced on the protesters with pepper spray, paintball guns full of chemical suppressants and stun grenades — either percussion or flash-bang grenades, both of which are used to disorient targets — that they hurled into a mostly peaceful crowd flecked with occasional anarchist rock-throwers.