The part of the experiment that is missed is that the monkeys have no structured set of chronology, while government is designed to created a trail of history regarding what happened when and what the result was. The monkeys remember, but don't communicate beyond the beating, don't have ancillary knowledge of the water cannon (you know, written stuff?) and are incapable of asking why and why not. Also, it focuses only the brutality of the situation leading to the self-defeating prophecy, while human interaction, even at a bureaucratic level, is never that straightforward and humans also have a higher chance of ignoring the barbs of others to accomplish something. A lot is accomplished because people do something while deflecting massive criticism.
Cutting away to the police officer beating an individual with a war protest sign behind it was heavy handed on the presentation part. It creates context behind a scene that, in itself, has nothing but ambiguity. No narrative. If we are to assume the assumed premise of the film by the juxtaposition, we are falling victim to the film's criticism of "monkey see."
Additionally there's no explanation for the water cannon, metaphorically.