Teaching will age you. Current high school students and college underclassmen, for example, don't remember 9-11. One such moment that stood out in my teaching career was making a reference to Rodney King and then having to explain who Rodney King is to a group of legal adults. The saddest part was not how old I felt at that moment, but that my students simply could not understand why it was a big deal. The idea that a video of police beating up a black man – who didn't even die – was ever novel or unusual to Americans is, for today's young adult, baffling. They made the same face they make when I tell them that television only had three channels at one point.

We have a problem. We have always had a problem, in fact. The violence isn't new, but the cameras are everywhere to record it now. What happened in Dallas last week was a sadly predictable reaction in a nation that already knows well the amount of havoc one angry young male with a high powered firearm can cause. I suppose young black men can only watch so many videos of police killing people who look like them with no greater social response than excuse-making, justifications, and victim-blaming before one person in a nation drowning in guns is going to decide that killing cops is a valid response.

I keep holding out hope that we will learn something from this, that police can say to themselves "All those Dallas officers wanted was to do their job and go home alive at the end of the day" and have some moment of inspired transference wherein they realize that every black person they pull over in a traffic stop wants the same. I keep holding out hope that empathy is an emotion that any adult is capable of experiencing if it is encouraged. I'm not giving up yet. But it's not looking good.

For now, I'm going to do what I do best and try to subject the problem with the way we respond to these incidents to some cold logic.

As this radio personality angrily but succinctly pointed out last week, the basic problem here is the culture of mutual protection that pervades law enforcement. There is never an incident of police conduct that other police do not defend. If every single incident is met with excuses and rationalizations, if there is never an incident that other police look at and collectively say "Holy crap, that's totally unacceptable," then we have to conclude that according to police, no police officer has ever done anything wrong. If they're never willing to look at one another and say "That's wrong" or "You suck at your job," that implies that police are right 100% of the time. That's flatly illogical, and any American in any profession can reach that conclusion without difficulty because the idea of 100% of any group of people being competent is ridiculous on its face. Are 100% of teachers good teachers? Are 100% of your co-workers good at their jobs? Do 100% of cabbies drive well? Are 100% of salesmen honest? Are 100% of stylists giving good haircuts?

OK. So with just the briefest application of logic we can reject the idea that 100% of police are good at their jobs, and that 100% of the actions police take are appropriate. It's totally implausible. Any profession has malingerers, assholes, malcontents, sociopaths, and incompetents. This includes police.

If most cops are good cops as we are repeatedly told – and statistically that's true, as most departments have a few officers who account for the majority of complaints – then it is time for the Good Cops to stop participating silently in a broken system. It's time for Good Cops to do something about Bad Cops. Enough with the Wells, the Buts, and the Umms, the excuses and the justifications and the sanctimonious explanations of why black men never, ever perform the correct steps in the correct order to avoid getting shot while Dylann Roof can kill nine people in a church and the police take him to Burger King on the way to jail because he wanted a Whopper. Public protesting of the actions of police is less likely to motivate changes (and will do so a lot more slowly) than Good Cops refusing to condone further the behavior of their Bad colleagues. I defy anyone to come up with a more effective way to restore the trust and confidence that the public no longer has in law enforcement than following up a video like the death of Eric Garner, for example, with the chief of police saying "This is unacceptable and we will do whatever is necessary to make sure it never happens again" and following through on the promise. Instead we get boilerplate bromides about the police investigating themselves (inevitably determining that they did nothing wrong) and reserving judgment until all the facts are in, a time period that happens to coincide with the time required to put the character of the dead man on trial and explain why his death was his own fault. Until all the Good Cops can look at these videos and say "This is wrong, period" there can be no trust and no confidence. If police think the police are right every time, what does that say about their judgment?

Nobody's promising that it will be easy. We've all seen Serpico. This is, in the literal sense, a matter of life and death. If you're a Good Cop, now's an excellent time to prove it. Police are always telling the public that policing – maintaining order, preventing crime – starts with the community and the citizen. Imagine if they applied the same concept to themselves. If it's just a few bad apples…well, what's the second half of that saying?