This is the method used in dealing with elementary school kids: Instead of disciplining unruly and/or disruptive kids, they implement overly-strict rules that punish everyone preemptively.
It's easier than having to identify and punish the actual offenders.
As for the media's role, the public shares the blame on that score. What we now call TV news -- where most people get their 'news' -- was once set apart from entertainment and could pursue actual reportage. Now it is lumped into the same cost center and must meet ratings targets or people lose jobs.
So, local news' long-time mantra of "if it bleeds, it leads" is joined to "give the people what they want" and these tandem mindsets feed the public perception of an ever-more dangerous world even as crime rates fall.