For Christians across the nation and globe, the Christmas season is about glad tidings of joy and peace. But we must not forget that what accompanied the birth of Jesus - the "reason for the season" - was anything but joyful: King Herod's slaughter of male infants in Bethlehem.

Today, 20 centuries later, Christians along with other religious communities in Syria and Iraq, including Yazidis, Shi'a, Turkmen, and Shabak, face a new Middle East tyrant in ISIS. But unlike Herod, whose real aim was to destroy one child among thousands, ISIS's goal is to obliterate the communities themselves.

It is, in other words, genocide.

As we write, the State Department reportedly is on the verge of finding that ISIS is committing genocide against the Yazidis, a non-Muslim religious minority in Iraq.

We would wholeheartedly endorse that finding, which could make it easier for Yazidis to find asylum.

But what about others? What especially about the largest non-Muslim minority in the Middle East: Christians.

ISIS viciously persecutes Christians, yet inexplicably the State Department seems to be considering declining to designate Christians as victims of ISIS's genocide.

Such a thing would be a shameful mistake, a puzzling abdication of moral duty, and a monumental travesty of justice.

The 1948 Genocide Convention defined genocide as acts "committed with intent to destroy, in whole or in part, a national, ethnic, racial or religious group." Such acts include "killing members of the group; causing serious bodily or mental harm to [its] members; deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part; imposing measures intended to prevent births within the group; or forcibly transferring children of the group to another group."

The proof that Yazidis fit the definition of genocide victims is clear enough. Comprising about half a million people, Yazidis received national attention last year when at least 50,000 of them fled into the mountains to escape the horrors of ISIS, including rape and murder, torture, and enslavement. This month, the U.S. Holocaust Museum released a report stating that ISIS tried to prevent Yazidi births and convert children in its efforts to eradicate them.

But by all accounts, Christians as well as Yazidis have borne the worst brunt of ISIS depredations.

From summary executions to forced conversions, rape to sexual enslavement, abducted children to destroyed houses of worship, attacks on both of these communities have been part of a systematic effort to obliterate their presence from the Middle East. In addition, there is evidence of beheadings; crucifixions; assassinations of church leaders; kidnappings for ransom; destruction of monasteries, cemeteries, and artifacts; and theft of lands and wealth from Christian clergy and laity alike. And of course, there are ISIS's own damning statements taking responsibility for the mass murders and declaring its intent to eliminate Christian communities from its "Islamic State."

More than a decade ago, more than one million Christians lived in Iraq alone. Thanks in part to ISIS, fewer than 300,000 remain. If ISIS's goal is eradicating their presence, it is well on its way to success.

Pope Francis has called what is happening to Christians genocide. So have the U.S. Conference of Catholic Bishops and Christian leaders across the Middle East.

Why, then, would the State Department exclude Christians and others from designation as genocide victims?

One rationale for exclusion of Christians is that ISIS follows traditional sharia law, which recognizes Christians, as well as Jews, though not Yazidis, as "People of the Book," thus giving them a choice beyond death or conversion: paying a special tax for non-Muslims, the jizya, in exchange for protection.

This rationale is utterly at odds with reality. In practice, ISIS offers nothing of the kind. It flouts not only the most fundamental human rights, including the right to religious freedom, but every norm, standard, and rule of civilization. ISIS ultimately operates above all law, including Islamic law. It is a law unto itself.

The United States is rightly viewed as the world's historic refuge for the persecuted and especially those fleeing religious persecution. Our nation was founded by those escaping such persecution, and tens of millions of Americans are descended from those who came to our shores for precisely that purpose.

For the sake of this proud heritage and history, as well as simple humanitarian decency, our government must not turn its back on persecuted Christians or any other religious minorities during this, their maximum moment of need.

It is time to declare Christians as well as Yazidis and the other religious minority communities victims of genocide and help assist their resettlement. In this yuletide season, it is time to stand for the innocent targets of today's Herod, Christian and non-Christian alike, while they still live and their communities still exist.

Robert P. George is McCormick professor of jurisprudence and director of the James Madison Program in American Studies and Institutions at Princeton University

Mary Ann Glendon is the Learned Hand professor of law at Harvard University and former U.S. ambassador to the Holy See

Katrina Lantos Swett is the president and CEO of the Lantos Foundation for Human Rights and Justice