By now we've grown sadly accustomed to watching horrific videos. We've seen a police officer shoot a man named Daniel Shaver while he was crying and crawling on his hands and knees. We watched a police officer gun down Philando Castile in front of his girlfriend and her young child as he tried to follow the officer's confusing instructions. And this week brought us video of a civilian named Michael Drejka shooting and killing Markeis McGlockton after McGlockton merely shoved him to the ground.

All these men share something tragically in common: They were killed by cowards. They also have something else in common: Their killers are walking free.

Cowardice is not an accusation one should make lightly. It is perhaps the ultimate insult, often delivered by people who haven't faced danger themselves. But when a man panics in the face of risk and wrongly takes a life, cowardice is the explanation. Cowardice can have many causes, including an irrational, racist fear of black men or a simple lack of moral fortitude. And when it's on display, it can be ugly to see.

Over the past two years, as a senior writer at National Review, a gun owner, and a defender of gun rights, I have condemned each of these killings. Yet each time I write, I've received strong pushback. The theme is always the same: The cops were afraid. The man who killed McGlockton was afraid. How can we second-guess decisions made under duress, critics ask, when seconds count and lives could be on the line? This is the excuse juries use when they vote to acquit. It's the excuse law enforcement officials make when they refuse even to bring charges.

But we second-guess these decisions because the law requires us to. We also judge these decisions because respect for life and liberty demands it. No man or woman is required to be a police officer. No man or woman is required to carry a gun on their person. When you pick up a weapon, you are exercising a constitutionally protected freedom, yes, but you are also taking on an awesome responsibility. And the gravity of the responsibility requires an armed citizen – like a police officer – to tolerate a degree of risk and danger before he or she escalates to deadly force.

Any other rule reaches absurd (and deadly) results. This week, I was a guest on a talk-radio show when a caller earnestly tried to convince me that McGlockton's push justified deadly force. After all, he "could" have done worse. But where's the limiting principle? Every punch "could" do worse damage. Every kick "could" bring another. But here's the proper, default answer when the armed citizen or armed officer wonders what "could" happen next.

Risk it. Risk that next move. Be more certain before you take a life.

And what about the law? In reality, we don't need to reform it, we need to apply it. Specifically, in the context of police shootings and civilian self- defense, the fear of imminent death or great bodily harm that justifies lethal force has to be reasonable. That means law enforcement officials and juries are required to second-guess the decisions made under stress, and the fact of fear, by itself, does not exonerate the defendant. It only begins the inquiry.

It is simply a fact that the irresponsible or reckless exercise of any given freedom undermines public support for that liberty. Thus, those who support, say, the First Amendment should be among the most vigilant in exercising those rights virtuously. Those who support the Second Amendment should be unrelenting in preaching responsibility, prudence, and courage. Applying these principles to the McGlockton case, was it reasonable for Drejka to believe his life was in danger after one shove? How about when McGlockton backed away the instant Drejka brandished his gun?

This month, The Washington Post published an account of a true act of heroism. Two armed citizens confronted a man who opened fire on a restaurant. They showed courage. They ran to the sound of gunfire. They showed prudence. They took great care in fixing their target and making sure he was a threat before they opened fire. I'd argue that they represent the true face of lawful American gun ownership. Survey the crime statistics, and you'll see it's remarkably rare for concealed-carry permit holders to commit crimes. The best available evidence suggests they're more law-abiding, even than the police.

Cultures are enforced by norms, both legal and moral. Want to defend the Second Amendment? Uphold the original intent of the Constitution, yes. But you must do more. Give cowards no quarter, in our culture or in our courts.

David French is a senior fellow at the National Review Institute.