As events in Ferguson, Missouri unfold, several observers have noticed that "this time is different." Unlike during past instances of police officers killing or assaulting young black men in suspicious though not yet demonstrably criminal circumstances, some prominent conservatives are doubting the official police narrative or criticizing their militarized response to protesters. Some attribute this to a growing libertarian influence in the GOP, and it's no accident that Senator Rand Paul of Kentucky has offered one of the strongest calls for police reform.

My colleagues Peter Beinart and Ross Douthat persuasively argue that falling crime has made the American public less inclined to reflexively side with police, which has changed political incentives. Douthat posits that this is a generational shift.

But when it comes to how reflexively or instinctively cops are presumed to be truthful and honorable, the importance of video shouldn't be discounted. A generation ago, footage of police officers in the Deep South turning snarling dogs and firehoses on Civil Rights protesters made a deep impression on my parents, even though they grew up a continent away in an overwhelmingly white suburb where their personal experiences would've made police behaving that way seem unfathomable. Watching Jim Crow's enforcers with their own eyes couldn't be ignored. If anyone thought in 1991 that such brutality was a vestige of the past, or something that could only happen among racist cops in the South, the Rodney King tape disabused them of that notion, kicking off an era of cheap, increasingly ubiquitous recording equipment that was bound to capture more police misbehavior.

Of course young people growing up with YouTube will trust police officers less. The many videos of brutality don't lie—and they confirm that, sometimes, cops do lie.

Even more often, they hold their tongues.

"Most police officers are good cops and good people. It is an unquestionably difficult job, especially in the current circumstances," Senator Paul wrote in his op-ed. "There is a systemic problem with today’s law enforcement." He went on to talk about police militarization. But there is another systemic problem in law enforcement. Even good people in uniform routinely fail to report on bad colleagues. They don't engage in certain unsavory behavior themselves. But when other cops do, they look the other way. Nearly every law enforcement agency in America has within its ranks an unofficial code of loyalty to good and bad officers alike.

This is evident in the Rodney King tape. As Peter Jennings said way back in 1991, it was "a story that might never have surfaced if someone wouldn't have picked up his home video camera"—a judgment he rendered, and that we all know to be true, despite the fact that there weren't just five officers beating on King, there were also numerous other police officers standing around watching. This is a pattern that repeats itself again and again in documented instances of police abuse. My colleague Ta-Nehisi Coates has addressed the canard that black people ignore black-on-black violence. I'd only add that I've heard a lot more denunciations of black-on-black violence from black people, black leaders—hell, even black rappers—than I've heard rank-and-file police officers denouncing "blue-on-black" or even "blue-on-white" violence perpetrated by fellow officers. The only such statements I can ever recall came from police brass under political pressure to distance themselves from underlings caught misbehaving. I don't necessarily think police officers are less likely than people in other professions to tell on misbehaving colleagues. But the stakes are rather different, and their job is to enforce the rules, even when fellow officers break them.