WASHINGTON — President Donald J. Trump has railed against undocumented immigrants in recent days, branding many of them «murderers and thieves» who want to «infest our country.» Not long ago, he referred to them as «animals,» although he insisted he meant only those in a violent gang.

Mr. Trump’s coarse discourse increasingly seems to inspire opponents to respond with vituperative words of their own, like Robert De Niro’s profane condemnation at the Tony Awards.

The politics of rage that animated Mr. Trump’s political rise now dominate the national conversation in the United States, as demonstrated repeatedly during the debate over his «zero tolerance» immigration policy that separated children from parents apprehended at the border.

«Unfortunately, we’ve seen a decline in civility and an uptick in incivility,» said Christine Porath, author of «Mastering Civility,» a book on behavior in the workplace. «It seems like people are not only reciprocating, but we tend to stoop lower rather than higher.»

Ms. Porath said the current harsh climate was affecting people beyond politics, injecting itself into everyday life at home and work. «We know that incivility is contagious,» she said. «It’s like a bug or virus. It’s not only when people experience incivility, it’s when they see or read about it.»

Mr. Trump’s descriptions of those trying to enter the country illegally have been so sharp that critics say they dehumanize people. This approach traces back to the day Mr. Trump announced his campaign for president in 2015, when he labeled many Mexican immigrants as «rapists.»

Mr. Trump recently recalled that controversy. «Remember I made that speech and I was badly criticized? ‘Oh, it’s so terrible, what he said,’ » he said with derision during a speech to the National Federation of Independent Business on June 19. «Turned out I was 100 percent right. That’s why I got elected.»

Mr. Trump has called Canada’s prime minister «weak & dishonest.» He has called journalists, lawmakers and political opponents «wacky,» «crazy,» «goofy,» «mentally deranged,» «psycho,» «sleazy» and «corrupt.» He has called some of his own appointees and Republican allies «very bad,» «VERY weak,» «failed» and «lightweight.»

Returning incivility with incivility has not always worked out well for his opponents. When Senators Marco Rubio of Florida and Ted Cruz of Texas tried it during the Republican primaries in 2016, it backfired.

«Only Trump can get away with being Trump,» said Jennifer Mercieca, an associate professor at Texas A&M University who has studied his language. «Any time that other people have tried to use ad hominem attacks or swear or whatever, it rings false. And other politicians tend to have more shame, so when they’re criticized they fold. And as you know, Trump doesn’t do that. And so because he refuses to be shamed, he can get away with sort of saying anything.»

Harsh discourse in American politics goes back to the fractious days of John Adams versus Thomas Jefferson. But rarely has the president himself set the tone the way Mr. Trump does. When President George Bush called Bill Clinton a «bozo» in 1992, it was seen as unpresidential.

Some liberals bristle at the idea that they should hold back in the face of what they consider an inhumane presidency. Jessica Valenti, a columnist for Guardian U.S. and the author of books on feminism, politics and culture, said restraint played into Mr. Trump’s hands. «Expecting those of us who are scared and angry over what our country is becoming to speak with civility is absurd — civility died the day Trump took office,» she wrote. «It’s like telling a woman to smile as she’s being sexually harassed on the street.»

One of the most sensitive debates generated by Mr. Trump’s family separation policy was the question of when Nazi comparisons are appropriate. When Michael V. Hayden, the former C.I.A. director under President George W. Bush, posted a picture of a concentration camp and wrote, «Other governments have separated mothers and children,» it prompted an exchange on CNN with the anchor Wolf Blitzer, who noted that his relatives were murdered in the Holocaust. He told Mr. Hayden, «As bad as this policy is, it’s certainly not Auschwitz.»

Two Holocaust survivors, however, posted a video talking about the impact of being separated from their parents. «Let’s be clear: We are not comparing what is happening today to the Holocaust,» they said. «But forcibly separating children from their parents is an act of cruelty under all circumstances.»

Jonathan Greenblatt, the chief executive of the Anti-Defamation League, an international group devoted to fighting anti-Semitism, said that everyone «should be extremely careful» with Holocaust comparisons but that «there are disturbing parallels that have touched a nerve.»

«Let’s not spend time drawing comparisons,» he added. «Instead, we should focus all of our energy fighting for a more moral set of policies today.»

The politics of rage dominates anational debate