Police departments, like most of our institutions, are mere shadows of what they were 30-40 years ago. Diversity and multiculturalism, coupled with a diminished qualification standard, are at the root of the problem. Most officers today wouldn’t have been considered for the job decades ago.
About 45 years ago is when I first saw the "Us against Them" mentality come in to play in police-citizen interactions. Now it seems to be a required doctrine for the job.