Why would anyone ever speak to a police officer?

The officer's claim that he felt threatened is a huge reach, and that seems to be the claimed impetus for the arrest. Not all police are reasonable. Not all prosecutors are reasonable. Do police ask that surveillance cameras be turned off whenever they enter a store? Filming a police officer doing his job properly can be good for the police. Filming an officer who does his job improperly can be a service to the public.