A newly sinister note of violence has crept into Donald Trump’s rhetoric recently, as witnessed by his Veterans Day speech at Stevens High School in Claremont earlier this month.

You may find that hard to believe, given that the former president has already attempted to overthrow the legitimate government of the United States and routinely advocates executing drug dealers and shooting shoplifters. Yet, it was unmistakably there.

Trump vowed to “root out the communists, Marxists, fascists and the radical left thugs that live like vermin within the confines of our country.” In this telling, Trump’s enemies — not China, not Russia, not Iran — now constitute the most pressing problem America faces. “The threat from outside forces is far less sinister, dangerous and grave than the threat from within. Our threat is from within,” he claimed.

To be clear, this kind of language expressly echoes the monstrous faith of Hitler and Stalin and Pol Pot that annihilating enemies real and imagined can enforce ideological or racial purity. Vermin was one of Hitler’s favorite terms for Jews. And if you doubt that the language precedes the deed, dig out a copy of Mein Kampf. Many millions paid with their lives in the previous century when such explicit warning signs were ignored.

When critics pointed this out, Trump spokesman Steven Cheung labeled the assertion “ridiculous” and suggested they were overwrought. He then proceeded to confirm their worst fears. Their “entire existence will be crushed when President Trump returns to the White House,” Cheung told The Washington Post, before amending “entire” to “sad, miserable” existence. Either way, we get the point. These are not merely political opponents to be defeated, but enemies to be crushed.

Along the same lines, Trump recently told a right-wing website that undocumented immigrants are “poisoning the blood of our country.” Aides have disclosed plans, should Trump be elected president again next year, to round up millions of migrants in huge concentration camps and unilaterally deport them without due process hearings, The New York Times has reported.

Once such camps are established, it’s not a big leap to foresee that the “vermin” will join the migrants there. And if they can’t be deported? Well, the fate of vermin is to be exterminated.

We are not suggesting by any means that the vast majority of the crowd in Claremont, or Trump supporters in general, embrace the implications of Trump’s remarks or even are aware of them. Many of his supporters have long reveled in his “rough around the edges” persona, which depends heavily on his willingness to voice the outrageous. But this kind of rhetoric is qualitatively different. Language that dehumanizes groups of people and reduces individuals to loathsome stereotypes creates the soil in which horrors can take root and grow. This is a line that has to be drawn.

If you take comfort in the conviction that America is too decent, too tolerant, too committed to the rule of law to countenance any widespread persecution, the lesson of Nazi-era Germany is that any nation, no matter how cultured and well ordered, can become collectively deranged.

Trump is now laying out the path ahead if he succeeds in regaining power. There’s no excuse for not recognizing where it might lead, and no excuse to think you might not be caught up in it. There is much wisdom in the words of the Roman historian Tacitus: “Once the killing starts, it is difficult to draw the line.”