Not an US citizen but the issue with police is that for a start in every country that I know of, they are not your equal law-abiding citizen when wearing a uniform. Most of the time, they have law tools allowing them to arrest, fine you, etc. if they feel threaten, being at risk or insulted and only by their own appreciation. Nobody will review their appreciation and to contest such case, it fail on you side to make all the necessary steps to contest (best case scenario if you don't end up dead on the street).

So being live streamed without consent is first and foremost a citizen tool to overwatch the police's action and honestly you don't have anything else allowing to do that in real-time. Policemen are not backed in a corner when filmed, they are acting in broad light. It may seems adversely but police proved since decades that they always took the violent path when interacting with people one way or the other and giving policeman the power to take it down on people profiled or randomly is a repeated proof. If great powers comes with great responsibilities, an uniform does not seem to come with a way to enforce the later.