Imagine that today’s Republican contenders were running for president in 1920. In 1917, the Bolsheviks had taken power in Russia, and sworn to export revolution across the globe, if necessary by force. They were joined in that desire by the Communist Party USA, a disproportionate percentage of whose members were Eastern European immigrants, especially Jews. In the 1920s, the Yiddish-language Morgen Freiheit, was the largest communist newspaper in the United States.

Immigrant radicals were already notorious for committing acts of terrorism. In 1901, Leon Czolgosz, born to an immigrant family from what is now Belarus, had assassinated President William McKinley. In 1920, followers of the Italian immigrant anarchist Luigi Galleani bombed Wall Street, killing 38 people, and tried to assassinate A. Mitchell Palmer, the attorney general of the United States.

The federal government responded with the Immigration Act of 1918, which empowered the federal government to deny radical immigrants entry to the United States and to deport those already in the country. Beginning in November 1919, Attorney General Palmer authorized a series of raids against the Union of Russian Workers and other radical groups. In New York City alone, more than 5,000 Russian immigrants were arrested.

But the government didn’t stop there. Eastern and Southern European immigrants, argued the Immigration Restriction League, weren’t only stealing American jobs and undermining American culture, they were threatening American security.

Allowing them to stream unchecked into the United States was madness. So in two laws, in 1921 and 1924, Congress shut down Eastern and Southern European immigration almost completely, thus unknowingly sentencing large numbers of Eastern European Jews to their death.

The arguments the Immigration Restriction League made back then mirror the arguments Republican presidential candidates are making about Syrian refugees today. Since September 11, the United States has accepted 784,000 refugees, not a single one of whom has committed a terrorist act in the United States. The Boston Bombers, contrary to what some politicians have claimed, were not refugees. Their father gained asylum after having already been in the United States.

The difference is crucial because refugees can’t get into the country without an arduous screening process. As the Migration Policy Institute’s Kathleen Newland notes, the “refugee resettlement program is the least likely avenue for a terrorist to choose. Refugees who are selected for resettlement to the United States go through a painstaking, many-layered review before they are accepted. The FBI, Department of Homeland Security, State Department, and national intelligence agencies independently check refugees’ biometric data against security databases. The whole process typically takes 18-24 months, with high hurdles for security clearance.” The screening process for Syrian refugees is particularly grueling, so grueling, in fact, that since that country’s civil war broke out four years ago, only about 2,000 Syrian refugees have been admitted into the United States.

Despite this, the GOP presidential contenders have reacted to the Paris attacks with an eruption of nativist hysteria. Mike Huckabee has said that if House Speaker Paul Ryan doesn’t push through legislation barring Syrian refugees from the country, he should resign. Chris Christie has said he would not even accept a “three year old orphan” from Syria. Ted Cruz has said Syrians should be resettled in “majority Muslim” countries, which offers a clue as to his real motivation. If Syrian refugees really pose a grave terrorist threat, then it’s just as dangerous to resettle them in “majority Muslim” countries as in majority Christian ones. But if you’re using the pretext of a terrorist threat to bar Muslims from the West, Cruz’s argument makes perfect sense.

The doctrine the GOP candidates are peddling now is the same one the Immigration Restriction League peddled a century ago: collective punishment. Could a Syrian refugee commit terrorism today, just as some Russian and Italian immigrants did in the early twentieth century? Of course. Should the United States make its refugee vetting system as foolproof as possible? Of course. But punishing vast numbers of innocent, desperate people for the potential crimes of a tiny few is utterly immoral. And in other contexts, it’s a logic the Republican candidates would never consider. After all, if it’s worth barring Syrian refugees from the country because a few might be terrorists, why not bar Americans from owning guns because a few might use them for mass murder? Why not bar introverted, video game-obsessed, teenage boys from movie theaters? Why not bar immigration by right-wing Norwegians, since in 2011 one of them committed a terrorist attack almost as gruesome as the one committed last weekend in Paris.

Politicians usually propose collective punishment against groups they have already dehumanized. That’s why immigrant Catholics bore the brunt of America’s fears about terrorism and radicalism a century ago even though plenty of native-born Protestants harbored communist or anarchist sympathies and committed violent acts. And it’s why today’s Republican candidates are demonizing Syrian refugees even though white supremacists and other non-Muslim fanatics have killed almost twice as many people in terrorist attacks on American soil since 9/11 as have violent jihadists.

Decades from now, American schoolchildren will view the 2016 GOP candidates’ response to Syrian refugees in much the same way American schoolchildren now view the Palmer Raids: with disgust. They’ll also learn that Barack Obama responded to that hysteria by declaring that in the United States, “we don’t have religious tests to our compassion.” And they’ll understand why he was a great President of the United States.