The global refugee crisis is one of the top issues facing the United Nations as it meets in New York this week. Countries are under pressure to step up their commitments to accept more of the 19 million refugees and asylum-seekers currently flung far from their homes, and alleviate one of the world’s most pressing crises.

The current president of the United States is chairing one of those meetings. The man who could be the next president of the United States is busy comparing refugees to poisonous snakes. His son compares them to Skittles.

Donald Trump’s (and Donald Trump Jr.’s) xenophobic rhetoric isn’t new. But they’re doubling down in the home stretch of the campaign. Just as, internationally, momentum is gaining to welcome refugees, the US — historically a beacon to the world — is hearing a man who might be our next president dehumanizing them.

It would be tragic if the US turned away now.

Donald Trump’s dehumanizing rhetoric goes way beyond his son’s Skittles tweet

Donald Trump Jr. compares refugees to poisonous Skittles: If three could kill you, why risk eating an entire handful?

His father — the one who’s actually running for president — uses even less benign metaphors.

For the past year, since the world started paying serious attention to the plight of Syrian migrants, Trump has been warning his devoted followers that letting refugees in would make the US vulnerable to new terror attacks. In speech after speech, he’s falsely claimed that the US wasn’t vetting the would-be immigrants, lied about the numbers the administration has committed to taking in, and warned that “This could be the all-time great Trojan horse.”

One of the greatest hits of Trump’s stump speech — a bit so classic that, by this point in the campaign, he’s taken to making his audiences beg him to repeat it — is the recitation of the lyrics of “The Snake.” It’s a story of a woman who takes a “poor, half-frozen snake” into her home, only to have it give her a lethal bite. The punchline: “You knew damn well I was a snake before you took me in.”

The message (not as the songwriter, civil-rights activist Oscar Brown Jr., intended it, but as Trump intends it) is perfectly clear: Just because someone is half-dead and suffering doesn’t mean they wouldn’t kill you if given the chance.

Both of these metaphors have been part of the Trump experience for a while, but he’s relying on them more than ever. His stump speech Monday night was almost entirely about the nexus between immigration and national security: the issue that launched him into the spotlight, and that has always been more developed than any other policy he’s addressed during his campaign.

Trump’s closing argument, with 50 days left in the campaign, is that America is under attack from immigrants who may look harmless but are going to overrun the country and kill Americans if they’re allowed to arrive, and that only Donald Trump can stop them.

Compared to these metaphors — an invading army, a poisonous snake — likening refugees to candy seems fairly benign.

America’s refused refugees before — to the nation’s ongoing shame

For 70 years, it’s been a fundamental international principle: countries have a moral obligation to accept refugees fleeing persecution and imminent danger. The US has been a world leader in resettling refugees: Historically, half of all refugees who’ve been permanently resettled in a distant country have come to the United States. America is a beacon to the world.

That wasn’t always the case. "The American commitment to bring refugees to the US really is birthed in the post-World War II era," historian Carl Bon Tempo told me last year.

There’s a reason for that. In the post-World War II era, and ever after, America’s struggled with ongoing guilt and shame about what happened the last time it ignored refugees’ plight: the 1930s.

US Jan 20 ’39: Should the US government permit 10,000 mostly Jewish refugee children to come in from Germany? pic.twitter.com/5cFs5RabQn — Historical Opinion (@HistOpinion) November 17, 2015

In early 1939 — before the start of World War II, but when it was entirely clear that Germany under Hitler was persecuting its Jewish population — the American public opposed a proposal to bring 10,000 Jewish refugee children to the US by nearly 2-1.

That spring, a bill to resettle 20,000 Jewish refugee children in the US quietly died — despite the fact that 1,400 Americans had written letters to Congress offering to take in a refugee child. In addition to political inertia, the restrictionist argument that “20,000 charming children will all too quickly grow into 20,000 ugly adults” was simply too strong.

In 1939, the St. Louis, a ship of 935 people — almost all of them German Jews — attempted to land in Cuba, to seek refuge from the Nazis while they finalized their visas for the United States. Cuba said no, and the US refused to intervene on their behalf. When the St. Louis turned away from Cuba and started sailing north, not only did US officials announce that she ship wouldn’t be allowed to dock in America, but it sent Coast Guard boats to tail the St. Louis as it approached US waters to drive home the point.

The refugees were ultimately resettled in Western Europe — many of them in countries that would later be invaded by the Nazis during World War II. Of the St. Louis’ 935 passengers, 254 were killed in the Holocaust.

The current refugee crisis has tested the world’s capacity to give them new homes

There are nearly 20 million refugees and asylum-seekers around the world. And most of them are living in a dangerous limbo.

Over the past few years, millions of people have been pushed to flee their countries; many because of the Syrian civil war, others because of renewed flare-ups of ongoing crises in Afghanistan, South Sudan, and Myanmar. But as the number of people seeking refuge elsewhere has grown, the willingness of other countries to resettle refugees and help them begin new lives has, if anything, shrunk.

The current crisis has tested the strength of national and international institutions.

The Syrian refugee crisis has tested the US’s ability to accept and resettle refugees — not because it’s impossible to screen refugees for security risks, but precisely because the US has been so careful and thorough in doing so. It takes about two years for the US to accept a refugee from Syria; for years, despite a theoretical commitment to prioritize Syrian refugees, the US was only letting in a couple hundred a month.

The commitment to vet Syrian refugees for “poison” threatened to get in the way of the moral commitment to welcome people fleeing danger. (That’s finally changed in spring of 2016, allowing the US to meet its goal of settling 10,000 Syrian refugees in the past fiscal year; Germany, a country less than a third the size of the US, has committed to accepting 800,000).

It’s an even bigger problem for the European Union. The number of refugees seeking asylum in Europe over the past few years has tested not only the ability of individual countries to accept and tolerate refugees, but also the idea of a unified Europe itself.

Countries are abandoning the EU’s policy of internal open borders, sometimes closing them without notice to impede the refugee flow; nations in Northern and interior Europe have (for the most part) done very little to alleviate the strain on countries like Greece and Italy where thousands of refugees might land on any given day. It’s led to the rise of anti-immigrant politics from the UK to Germany to Hungary. It’s challenged the idea that an integrated Europe can face challenges as a continent.

It’s not just the Syrian refugee crisis testing these commitments. The US has detained thousands of Central American families coming to the country to seek asylum. Kenya is trying to close the largest refugee camp in the world — and (allegedly) forcibly expelling its residents — even as South Sudan’s renewed political crisis has caused the number of South Sudanese refugees there to top 1 million.

Last spring, ships of Rohingya Muslims — fleeing persecution in Myanmar (a country that had stripped them of citizenship and the right to vote) — drifted at sea for several days between Indonesia, Malaysia, and Thailand, with each country’s government initially rejecting them. The Rohingya were ultimately accepted, but their future in the country remains deeply uncertain.

The international community is beginning to take the crisis seriously — and leaders are shaming each other into stepping up

It’s far too soon to expect the global refugee crisis to be resolved anytime in the near future, but world leaders are at least finally saying the right things.

On Monday, during the opening of the 2016 UN General Assembly, the world body held its first Summit on Refugees and Migrants (with the focus on refugees). At the meeting, diplomats and world leaders ratified new principles, but notably don’t set any standards for how many refugees rich countries should be obligated to resettle.

On Tuesday, meanwhile, President Barack Obama himself is chairing a “leaders’ meeting” on refugees: a not-so-subtle attempt to shame countries into committing to resettle more people.

Obama is committed to accepting more Syrian refugees. The US announced earlier in September that, in fiscal year 2017, it plans to allow 110,000 refugees to settle in the US — an increase of more than 50 percent from just two years ago.

Of course, that commitment depends entirely on who wins the November election. Trump has promised, time and again, not to uphold it. He’s promised to put “extreme” amounts of effort into vetting refugees, while cutting spending on refugees to help disadvantaged US citizens — a combination that makes it hard to imagine how much of the US refugee program could survive at all. Many Republican governors, meanwhile, have gone to court to try to prevent Syrian refugees from being resettled in their states.

The fact that the current US president is chairing a meeting to urge leaders to accept more refugees, as a man who wants to succeed him is running on the principle of shutting our doors to them, is certainly a useful contrast. But the timing is tragic.

The UN summit and leaders’ meeting represent a growing international awareness that when it comes to accepting refugees, politicians aren’t just accountable to domestic public opinion.

To the extent they’re accountable to the international community — that they are morally responsible for continuing to help humankind flourish — they carry a humanitarian obligation to help fix a crisis that has left 19 million people in limbo. And they carry an obligation to the world’s long-term security to alleviate the regional instability that millions of displaced people create, and the danger posed by people who feel that no one in the world cares for them.

The world is beginning to wake up to this. The US is threatening to step away. Donald Trump’s refugee paranoia, his Trojan horses and snakes, and his son’s poisonous Skittles might resonate with his supporters. But they threaten to hollow out a core American ideal.