Often credited to the French philosopher Voltaire but actually penned by his biographer Evelyn Beatrice Hall, the phrase is almost universally known: “I disapprove of what you say, but I will defend to the death your right to say it.”

Misattribution does not diminish the power of the words. The idea matches the U.S. Constitution’s First Amendment, arguably the most important principle underpinning American liberty.

In the wake of the assassination of conservative advocate Charlie Kirk, a question troubles my mind.

Why is it that so many Americans no longer believe in the First’s principles?

Instead, millions of us have retreated behind our self-selected barricades and berate and threaten with astonishing anger and hostility those who dare think differently. The left does it. The right does it. Is it any wonder political violence is rising?

I’ve seen a lot of sunrises and America was never a perfectly peaceful place for politics. I remember President Kennedy’s murder. Robert Kennedy. Medgar Evers. Martin Luther King. The violence virus is not new.

Yet it seems different today. We could be comforted back then, blaming crazy loners. Now the hideous messages are everywhere. For a lot of it — not all, but a lot — I blame the cesspool of social media which encourages irresponsible rhetoric and isolation.

In the hours following Kirk’s murder, I decided to monitor my own Facebook feed. It includes the usual mix of family, real friends, acquaintances, professional networks and some of those “fake” friends one occasionally accepts in a weak moment. Here’s a sampling of what I found, either words posted by someone in my network or a meme or repost they passed along. Some of this is strong stuff and I apologize in advance. But I believe we all need to see what’s there, coming from people we know, and think hard about that. Here goes.

• “They wanted a prayer for Charlie and a leftist shouted No, No, No. Then came yelling. They showed you who they are. They can’t be civil or respectful. GFY!!” (Figure out for yourself what that stands for.)
• “Kirk is dead and I have no sh— to give.”
• “It’s obvious violence is a feature of the left, not a bug. After a certain point, you can no longer reason with people.”
• “We aren’t one people are we? The truth is we haven’t been for some time now, and there is really no point in pretending anymore, if there ever was. We are two very different peoples. We may occupy the same piece of geography, but that is where the similarities seem to abruptly end.”
• “The Minnesota lawmakers were in fact attacked by a Trump supporter.”
• “I’m fairly certain it isn’t anyone supporting this administration who is attempting to politically assassinate people.”
• “Democrats own what happened today.”
• “Political violence isn’t un-American. It’s the American way.”

Thankfully, there also were more heartwarming comments.

• “I’m grieving us as a species tonight. Whether or not you agree with Charlie Kirk, he was a child of God.…Please, turn off the news streams and start collecting hugs. You’ve become too jaded.”
• “This is not OK from either side, ever.”
• “Have a cup of coffee with someone you disagree with. Purposely reach out and befriend people of different ideologies.…Maybe it’s time to unfriend or unsubscribe from some of the louder voices who seem to lack any sense of self-control or who ignore nuance.”
• “Let’s not let the absolute evil and violence we see every day online control our lives. Unplug and love your family, take your faith seriously.”
• “When the next disagreement comes — and it will — what will you stand for? What will you protect? What will you refuse to destroy, simply because someone believes differently than you?”

Political violence is not one-sided. Never was. That’s a fact. It can only be denied by willfully turning away from the truth.

Before Charlie Kirk’s murder there were two assassination attempts against President Trump. Before that Republicans were targeted at a congressional baseball practice. A Democrat state legislator and her husband in Minnesota were killed by a man with a hit list that included dozens of Democrat targets. The Democrat governor of Pennsylvania and his family were targeted in his home by an arsonist. Police thwarted a plot to kidnap the Democrat governor of Michigan.

Radicals, left and right, are choosing a path that mocks all that is enshrined in the Constitution, the document left to us by wise men who staked everything on their belief Americans could govern themselves and control their worst passions.

On the same day of the Kirk murder another school was shot up by a lunatic with a gun.

The next day America marked the 24th anniversary of the 9-11 attacks. Remember the sense of unity that immediately followed across the political spectrum? And how quickly — within weeks — it all began to evaporate again?

Shame on us.

There have always been differences. There will always be differences in this closely divided country. Which means we all have a choice to make. Will we cling to our side, exalting it as righteous while going blind to contrary facts, and demonize and dehumanize political rivals? Or will we accept each other’s differences and embrace again the constitutional system designed to peacefully settle those disputes? All the while treating each other not as mortal enemies, but as fellow Americans.

No, that won’t stop every violent nut with a gun. Or a hammer. But don’t elevate them as being representative of the rest of us. Their hatred does not have to be our hatred.

Hostility will never heal America. Unplug from the hate machine.

Bill Barth is the former Editor of the Beloit Daily News, and a member of the Wisconsin Newspaper Hall of Fame. Write to him at bbarth@beloitdailynews.com.