Fairly easy mission. Once you drive to the location of the demonstration just walk up and beat up a few of the demonstrators. Once you have beat 2-3 a riot will start at which point you can walk behind the gate and destroy the trucks. Beat and kill the security guard and he will drop a pistol. Use the red explosive barrels to destroy the trucks. If for some reason you don't have any barrels left or any ammo left you can simply just beat on the truck to destroy it although this takes much longer. Once it lights on fire get away or the incoming explosion will kill you. Once all the trucks are destroyed the trophy will unlock.