This article was originally posted at Providence.

If we needed conclusive proof of the degraded condition of America’s political leadership, we have it in the debate over the Syrian refugee crisis.

For the Republican Party and its conservative allies, this is their hour of shame. Last week 27 Republican governors declared that they would not accept any more Syrian refugees into their states. The Republican-controlled House of Representatives, by a vote of 289-137, passed a bill calling for the most stringent vetting process ever established for people fleeing a war-torn nation. Party leaders are repudiating President Obama’s call to accept 10,000 Syrian refugees over the next year. Their rationale is that terrorists will slip in among the new arrivals and carry out a Paris-style attack in the United States.

The Republican Party’s response is a toxic mix of fear, exclusion, ignorance, and irrationality. Although conservatives have good reasons to doubt President Obama’s grasp of America’s national security threats, none of them justify a posture of cynicism and denial toward this human tragedy.

FBI Director James Comey lit the bonfire with his congressional testimony last month, when he warned that background checks on Syrian refugees can be problematic because of the lack of good intelligence in the theater of war. “If someone has never made a ripple in the pond in Syria in a way that would get their identity or their interest reflected in our database, we can query our database until the cows come home,” he said, “but there will be nothing showing up because we have no record of them.”

Despite repeated claims to the contrary, none of the Syrian refugees have been linked to the November 15 Paris attacks. Nevertheless,Republican presidential candidates have seized upon Mr. Comey’s testimony to discourage or bar Syrian refugees from entering the country.

Donald Trump warns of a “Trojan Horse” strategy that would allow terrorists to hide among their number. “This could be one of the great tactical ploys of all time,” he says. Ben Carson compares the threat of militants posing as refugees to a “rabid dog” prowling the neighborhood. “You’re probably going to put your children out of the way,” he said. “It doesn’t mean that you hate all dogs by any stretch of the imagination, but you’re putting your intellect into motion.”

The intellect is the one human faculty in this debate that is not in motion. Rather, the capacity for reason and moral reflection—the qualities of leadership desperately required at this hour—seems caught in a vice grip of irrationality.

Mr. Comey’s testimony about possible “gaps” in intelligence is accurate—but, taken out of context, badly misleading. Those who are using it to ban all Syrian refugees ignore the singular fact that the United States already has in place the toughest vetting process for refugees in the democratic West—much more discriminating than Europe with its open borders.

Refugees are first screened by the UN High Commission on Refugees, and only a fraction of those are selected for possible entry into the United States. They are then vetted by the National Counterterrorism Center, the FBI’s Terrorist Screening Center, the State Department, and Defense Department, and the Department of Homeland Security (involving an extensive, in-person interview). The entire process takes 18 to 24 months.

Barely 1,800 refugees have been allowed into the United States since the start of the Syrian civil war in 2011, a conflict that has displaced over 11 million people. Most are elderly men, women, and children. Many of them—including Muslims, Yazidis, Christians, and Jews—have been targeted for extinction either by the Syrian regime or the Islamic State. Two percent of the Syrian refugees now in the United States are single men of combat age.

No immigration system is risk-free. To demand such a system would mean shutting down all immigration into the United States—and betraying our deepest political and religious ideals in the process.

Republican leaders and their conservative allies seem prepared to abandon one of the most consequential ideas in history: the belief in American exceptionalism. Since the founding of the republic, Americans have insisted that their national interests must be tempered by their moral and religious interests—by their Judeo-Christian tradition that refuses to separate justice from mercy. They point to this historic commitment to explain the United States as a powerful global advocate for human dignity, democracy, and human rights.

President Obama—and the liberalism in which he lives and moves and has his being—rejects American exceptionalism. This accounts for his refusal to act on behalf of the Syrian people when acting decisively could have averted much of the killing and carnage. This explains why the president has watched, with stoic indifference, the transformation of Syria into a living hell for its people. He has allowed Bashar al-Assad to continue his genocidal campaign. He has declined to establish safe havens for Syrian refugees. For the first three years of the civil war, Mr. Obama, for all his recent moralizing, allowed exactly 30 Syrians per year to enter the United States.

It is hard to think of a president less qualified to lecture the nation about its moral obligations than this one. It is even harder to recall a commander in chief more naïve—even delusional—about the threat of Islamic radicalism.

Yet none of this excuses the hysterical and morally debased response of the Republican Party and its conservative allies. The victims of the Syrian civil war—and there are so many children among them—face a future of despair and destitution. The conflict has created a vortex of human suffering not seen since the end of the Second World War. Indeed, the last time the United States ignored a refugee crisis of this scale was during the administration of another liberal Democrat, Franklin Roosevelt, a master at separating his personal political interests from larger moral concerns. The victims, of course, were the Jews of Europe, trying to escape the fires of the Holocaust.

Yes, it is an hour of shame, an hour when the conscience of a nation has succumbed to a spirit of cowardice and fear. “Send these, the homeless, tempest-tossed, to me,” wrote Emma Lazarus. “I lift my lamp beside the golden door.” As the tempest rages on, America’s lamp is dimming.

Joseph Loconte is an associate professor of history at the King’s College in New York City and the author of A Hobbit, a Wardrobe, and a Great War: How J.R.R. Tolkien and C.S. Lewis Rediscovered Faith, Friendship, and Heroism in the Cataclysm of 1914-1918.