Science Fiction is largely used as an allegory to explore the real human condition in a way that is parallel to political and cultural topics of the day without the inherent baggage that people would bring to exploring the real topic.
While the original quote and topic is about deploying a military as a policing force, it actually also holds true in the reverse as well, as policing forces shift towards an adversarial militarization against their community, leading directly to the issues you raised in the first comment about the failure of them to live up to the “protect and serve” motto.
While fictional events aren’t real, they are written by real people with views, desires and goals. Good writers will have internal consistency for their characters and try to ensure their external interactions have the authenticity of the ring of truth, because that’s how people will relate to the characters and story.
Good fiction is just a random meaningless story, it’s a platform for education and safe exploration of the real human condition.
Some human ones are also just actively really bad at it. As both a manager and applicant, I’ve seen they can hinder hiring good candidates.