"Which is worse? The wolf who cries before eating the lamb or the wolf who does not."— Leo Tolstoy
Police officers are supposed to be trained in crowd control. As such, the first rule of crowd control is to never act in such a way that the crowd perceives that action to be a threat as this action may cause the crowd to become riot. Clearly, this officers actions crossed that line. I believe that the action of moving the barrier a few feet was designed to create enough tension to justify the use of pepper spray or worse.