It was heartening to see members of Congress from both parties echo calls for unity following Wednesday’s attempted massacre.

Putting aside their habitual rancor, Democrats and Republicans joined together to emphasize that violence has no place in our politics.

There is no possible counter-argument, but let’s admit the ugly truth the pols won’t: This is all about the election of Donald Trump, and the unhinged vitriol that shadows him.

There is nothing bipartisan about the peculiar hate gripping significant slices of America. Breaking a major social taboo, elements of the left have openly put a target on a sitting president and too many mainstream Democrats have been silent.

Think Kathy Griffin’s severed head. Think Madonna telling a rally she thinks about blowing up the White House. Think Shakespeare in the Park using a Trump stand-in for Julius Caesar — and the audience loving the blood lust.

Did a single leading Democrat denounce any of these outrages as dangerous incitement? How about celebrated cultural figures or religious leaders or historians — did any blow the whistle and say this is a line we do not cross because we know that way lies madness?

If they did, you can count them on one hand. Words have consequences, and so does silence.

Where’s the left-wing media when it comes to the spreading maniacal expressions of Trump Derangement Syndrome? So eager to lecture Americans about how they should feel and what they should believe about every aspect of daily life, the media don’t have the moral courage to call out their own cultural warriors when they go off the rails.

Indeed, the collapse of media standards when it comes to covering Trump is, I believe, a significant contributor to the bitter political and cultural schisms roiling the nation. No political figure in modern times has taken such a vicious pounding from establishment organizations, and their bias will inevitably serve as a license for some people to act.

The hatred for Trump doesn’t stop with him. It often extends to his supporters in a trickle-down spasm of violence, and it was not happenstance that yesterday’s attacker was a Bernie Sanders supporter who went gunning for Republican members of Congress.

Conservatives invited to speak on college campuses are so routinely greeted with violent protests that it is no longer a big news story.

Nothing could be less classically liberal than silence by intimidation, yet many faculty and college administrators wink and nod, as if blocking someone else’s free speech is a new form of free speech.

Actually, it’s not new. Every fascist, authoritarian and tin-pot dictator in history has tried to shut down dissent. Have the educated elite forgotten everything they learned? Or do their enlightened politics justify any means necessary?

To be clear, the animal who pulled the trigger is solely responsible for his actions. But unless we find that James T. Hodgkinson suffered from an acute mental illness, I see him as a Kathy Griffin Democrat who turned her “comedy” into action.

A recent post on his Facebook page reads:

“Trump is a Traitor. Trump Has Destroyed Our Democracy. It’s Time to Destroy Trump & Co.”

Sadly, there is nothing unusual about those words. They are actually quite common these days.

I frequently get letters from Trump-haters saying something almost identical. He’s a bigot, he’s un-American, he’s a traitor — and so are you for supporting him.

I hope you die. I hope your children die.

Yes, Americans actually write those things to other Americans over political differences. And they sign their names, as if it’s normal.

Tragically, it is becoming normal, and so, in the words of the late Sen. Daniel Patrick Moynihan, we see first-hand what it means when deviance is defined down.

Numbed by repetition, we gradually come to accept the unacceptable. Little by little, the barrier island is eroded, then we are shocked when there is nothing to stop the storm surge.

This is not to suggest that hatred for political figures is limited to the left. President Barack Obama, as a black man, was many times the target of racial prejudice from people on the right.

Yet a major difference was that all major American institutions, and virtually the entire political establishment, denounced that despicable animus when it surfaced. A united front against open expressions of racism held its ground.

With Trump, just the opposite is happening. The rage over his election, instead of waning, continues to gather steam. The fervent desire to be rid of him and anyone who supports him is expanding into dangerous dimensions.

And now the first shot has been fired. Let’s pray it is the last and that America comes to its senses before it is too late.