Editor’s Note: Michael D’Antonio is the author of the book “Never Enough: Donald Trump and the Pursuit of Success” and co-author with Peter Eisner of “The Shadow President: The Truth About Mike Pence.” The opinions expressed in this commentary are the author’s. View more opinion articles on CNN.

CNN  — 

Reaching deeper into his bag of bigotry, President Donald Trump hauled out some old tropes to describe Baltimore as a “disgusting rat and rodent infested mess” and “very dangerous & filthy.”

Rodent. Rat. Infested. Filthy. Even casual students of history will recognize this vocabulary echoes the hateful terms used by notorious anti-Semites. Nazi propagandists used images of rats to depict Jews, and Nazi manuals – such as “The Jew as World Parasite” – described them as being “filthy.” A Nazi film called “The Eternal Jew” drove the notion of infestation home, emphasizing Jewish-borne contagions.

Prior to 2016, it would have been unthinkable for an American president to speak of any corner of these United States in such despicable terms, but in the age of Trump, we are governed by a chief executive who will stoop even lower in order to attack someone he perceives to be an opponent. In this case it is Rep. Elijah Cummings who, as chairman of the House Oversight Committee, has assumed the job of actually overseeing the Executive Branch.

Not content to just argue with a critic, Trump returned to his longstanding practice of flinging mud at everyone and anyone who dares to question the limits of his authority. Or, as The Baltimore Sun put it in a scathing editorial last night, “This is a president who will happily debase himself at the slightest provocation.”

It’s in line with his approach to always hit back “ten times harder” – a theme that first lady Melania Trump spoke proudly of at the 2016 Republican National Convention.

But, in reality, Trump doesn’t hit 10 times harder. He simply hits below the belt, undermining the integrity of the office he holds. Earlier this month, he brought his bigotry to bear against four female, non-white members of Congress, telling them to “go back” to whatever country they came from, even though all are US citizens and three are native born. Predictably, Trump loyalists took up the sentiment at his next rally, chanting “send her back” like a crowd of haters who were ready to chase their supposed opponents out of the United States.

Shocking as it may be to hear a president echoing language used by American nativists and the Nazis, it is more shocking still to recognize that this is nothing new. This is the same President who called protesting football players “sons of bitches” and has directed hatred at immigrants for years. Let’s remember, too, that Trump found “very fine people” among the neo-Nazis who marched in Charlottesville and who, for many years before he was elected, led the racist campaign to declare then-President Barack Obama illegitimate because he falsely claimed Obama was foreign born (a claim he only disavowed years later.)

As bad as his rhetoric is, the Trump administration’s policies are even worse. In at least one incident, a Texas-born teen named Francisco Galicia spent nearly a month in federal custody, during which time he lost 26 pounds. He was arrested after border agents stopped and asked for his papers. Among his valid identification papers, agents found an inaccurate Mexican visa which mistakenly stated Mexico as his country of birth. Given the choice, federal authorities chose to lock him up for several weeks, rather than release him pending further investigation.

US Customs and Border Protection and Immigration and Customs enforcement issued a joint statement, in which they said, “This individual provided conflicting reports regarding status of citizenship after being apprehended by U.S. Border Patrol and transferred into Immigration and Customs Enforcement Custody.” They went on to say they are still “researching the facts.”

Galicia’s arrest came as the President was announcing there would be big raids across the United States against immigrants who were in the country illegally (raids that ultimately only led to the arrest of 35 people) and the press revealed bigoted messages passed among current and former immigration officials who belonged to a secret Facebook group called “I’m 10-15.” The posts on this site included jokes about migrant deaths and sexist remarks about Democratic Rep. Alexandria Ocasio-Cortez of New York. Border patrol chief Carla Provost was even a member, and though she admitted as much to Congress, she said she had not seen the messages until the ProPublica investigation was published.

To date, Trump and those who defend them have insisted he is not a bigot. “I don’t have a Racist bone in my body,” Trump stated on Twitter. In fact, as the evidence mounts, his racism has become irrefutable and his willingness to insult his fellow Americans has become alarming. Instead of keeping the peace, the chief law enforcement official in the land seems to be provoking his fellow citizens with reckless taunts.

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    Thankfully, brave journalists like CNN’s Victor Blackwell are speaking truth to power. In a moving segment on Saturday, Blackwell reminded the President and his audience that Blackwell grew up in Cummings’ district – and that hard-working, patriotic Americans lived there, just as hard-working, patriotic Americans lived in districts represented by Trump supporters. As such, the President should treat all Americans – regardless of race – with the dignity that they deserve.

    While Blackwell’s words may not prevent Trump from saying or tweeting future insults, they did remind Americans of the duty they have under this new President. Throughout his life, Trump has demonstrated the worst of what resides in the human heart and challenged others to resist him and be better versions of themselves. Blackwell met that challenge, but we all must continue to do so – at least until Election Day 2020.