Anyone who has watched the English Parliament debate knows that — ceremonial forms of address notwithstanding — they can be a fairly raucous bunch, routinely shouting down opposing speakers, yelling out, “Hear, hear!” and even booing with some regularity. This includes events at which the prime minister speaks before Parliament.

By contrast, debate in the United States Congress tends to be a comparatively staid and polite affair. (There have been notable exceptions. For example, in 1856, then-Rep. Preston Brooks, a pro-slavery Democrat from South Carolina, assaulted then-Sen. Charles Sumner, an abolitionist Republican from Massachusetts, hitting him repeatedly in the head with a heavy metal-topped cane, nearly killing him.)

Opportunities for the president of the United States to address Congress are treated as events warranting the greatest decorum. Consider 2009, when then-President Barack Obama addressed a joint session of Congress to defend his health care proposal. Joe Wilson, a Republican representative from South Carolina, infamously yelled out, “You lie!” This outburst was viewed by politicians (on both side of the aisle) and pundits alike as a grievous breach of propriety. Wilson apologized to President Obama and received an official reprimand by the House of Representatives.

As with so many other things, the courtesy and professionalism we expect of our elected officials is waning in the era of President Donald Trump, replaced by unceasing ire and outrage. This week’s State of the Union address was a sad example. Some Democrats such as Reps. Maxine Waters and Alexandria Ocasio-Cortez simply refused to attend. Other Democrats refused to stand when the president entered the chamber. During Trump’s speech, large numbers of Democrats yelled loudly to interrupt him. House Speaker Nancy Pelosi, in a shocking departure from protocol, did not introduce the president with the traditional honorarium — “I have the high privilege and distinct honor of presenting to you the president of the United States.” Instead, she said merely, “Members of Congress, the president of the United States.”

Pelosi then mumbled to herself, chewed her lip, rifled through papers and made sourpuss faces throughout the entire speech. But the grossest breach of professional etiquette was at the end of Trump’s speech. As soon as the president concluded, amid the applause from (most of) those in attendance, Pelosi made a point of standing up, ripping her paper copy of Trump’s speech in two and tossing the pieces on the desk in front of her in an open gesture of disgust.

The social media universe went nuts, and it was not just Republican and conservative viewers who were appalled. A number of self-described Democratic voters called C-SPAN to express their disapproval of Pelosi’s antics. George Washington University law professor Jonathan Turley (himself a Democrat) issued a scathing condemnation of Pelosi’s conduct, calling her behavior “extremely petty and profoundly inappropriate”: “Pelosi seemed to be intent on mocking President Trump from behind his back with sophomoric facial grimaces and head shaking, culminating in her ripping up a copy of his address. … (S)he tore up something far more important than a speech. Pelosi has shredded decades of tradition, decorum and civility that the nation could use now more than ever. … If Pelosi cannot maintain the dignity and neutrality of her office at the State of the Union, she should resign as the speaker of the House of Representatives.”

Democrats’ excuse, of course, is that they despise Trump, that he has been impeached (“for life,” in Pelosi’s words), and that he does not deserve their respect.

There are at least two problems with that rationale. First, it is the office that warrants respect, whatever one’s differences may be with the person who occupies it.

But more seriously (in my view, at least), congressional Democrats have let their loathing of Trump spill over into their views of Americans generally. Much has been made of the fact that Democrats in attendance refused to stand or applaud in response to the good economic news of record-low unemployment rates for black and Hispanic Americans, veterans, women and the disabled; record-low rates of poverty for black Americans; and a trade deal that enjoys the support of America’s labor unions. Nor did Democrats show any sympathy or support for Janiyah Davis, a fourth grader and the child of a single mother, for whom Trump announced an Opportunity Scholarship; or for the family of Rocky Jones, murdered by an illegal immigrant who was shielded from deportation by sanctuary policies.

Minorities, women, union workers, single parents — these are supposed to be Democrats’ natural constituencies. If you cannot celebrate the betterment of your fellow citizens’ circumstances because they were improved by policies advanced by your political opponent, then you are an ideologue and a fraud.

It’s unclear whom Democrats think they are winning over with this self-serving petulance. There is already a #WalkAway movement of disgruntled former Democrats. And African American activist Candace Owens, with her “Blexit” advocacy, is peeling away black support from Democrats. Owens argues that Democrats don’t really want minorities or the poor to succeed; their behavior at the State of the Union makes her claims that much more credible.

We are still far from the acrimony that prompted Preston Brooks to attempt the murder of Charles Sumner in 1856. But the Wikipedia entry states that the attack “contributed significantly to the country’s polarization over the issue of slavery” and is considered a precursor to “the ‘breakdown of reasoned discourse’ and the use of violence that eventually led to the American Civil War.”

It is not absurd to worry whether the ongoing breakdown of political propriety and reasoned discourse in our own age poses a similar threat.