Racial tension between the police force and the communities they serve is an ongoing issue. The more a police department's diversity reflects that of the community, the easier it becomes for both to have a trusting, mutually beneficial relationship with one another. Inversely, the wider the gap in diversity, the wider the distrust on both ends.
Although some agencies may be making a significant effort to diversify their ranks, many are not. We need to hold departments accountable for their inability to fairly represent their communities.
Please refer to this study with detailed statistics on "The Race Gap in America's Police Departments": http://www.nytimes.com/interactive/2014/09/03/us/the-race-gap-in-america...