When Khizr Khan stood up to speak at the Democratic National Convention last Thursday, his family story was not widely known. Neither he nor his wife was a figure of public prominence, nor had he spoken at any major political events in the past. But, waving a copy of the United States constitution, Khan addressed Trump in evocative terms that resonated across the country, asking the GOP candidate if he had “ever even read the U.S. constitution” and telling Trump that he had “sacrificed nothing, and no one.”

The sacrifice that Khan was referring to was that of his son, Humayun Khan, an Army captain who was killed while stationed in Iraq in 2004. In the days since the DNC ended, Khan’s speech has dominated public discussion about the election campaign. He has promised to continue speaking out until the Republican Party leadership repudiates Trump for his proposed ban on Muslim immigration to the United States.

The irony of Trump’s proposals about Muslims is that they partly mirror the Manichaean worldview of terrorist groups like the Islamic State. Both effectively carve the world into a binary of Muslims versus non-Muslims, finding no space for complex identities like the Khan family that encompass both Islam and the West.

A few days after Khan’s speech, ISIS released its own view on the controversy in its online magazine Dabiq. Under a picture of Humayun Khan’s grave at Arlington Cemetery, a caption read simply: “Beware of dying as an apostate.” According to the worldview of the Islamic State, Muslims of any denomination who do not accept its rule — let alone those who join groups like the U.S. military — are considered traitors. Not only have they forfeited their Muslim identity, they are considered contemptible enough for their deaths to be mocked and celebrated.

But people like the Khans are not only loathed by Muslim extremists. Since Khizr Khan’s speech, Trump has made incendiary comments about his wife, while far-right media outlets and Trump campaign surrogates have begun publicly spreading dark conspiracies about Khizr’s alleged ties to the Muslim Brotherhood and other seditious foreign organizations.

The abysmal lack of evidence for these claims has been no barrier. The message this sends is that regardless of the grave sacrifices the Khan family has made for America, their foreignness will remain intact.

In this way, the messages of the Islamic State and America’s populist right reinforce each other. The Khans are “apostates” from Islam in the eyes of ISIS, but they are also not truly American in the eyes of a large political movement that has coalesced around the candidacy of Trump. Khizr Khan’s sacrifice, losing a son in an American war, has not been enough to inure him from charges of disloyalty. In a black and white world, he and his family fit in nowhere.

Following the controversy over Trump’s comments, the Republican Party leadership issued tepid statements reaffirming its support for military service members and opposition to religious tests in politics. But to date, few have taken any meaningful steps toward disavowing Trump’s candidacy over his rhetoric. Trump’s proposal to ban Muslims from the United States, which he recently claimed to have “expanded,” registers support from a near-majority of Americans according to recent polling.

While Khizr Khan’s DNC speech was inspiring, the abstract ideals he invoked so passionately seem almost quaint in front of these brute facts. Trump’s candidacy has proven that the power of mass politics, mixed with crude ethnic appeals, can challenge the traditional idea of a citizenship based on rights and responsibilities.

In the long term, this revelation could have dire consequences for political culture in the United States.

In the 20th century, small revolutionary movements frequently sought ways to upend the existing social order by “heightening the contradictions” within their society. The urgent question today is whether there is a contradiction between being a Muslim and an American, or a Muslim and a European. The apocalyptic grand strategy of the Islamic State, a desperate insurgent group operating over parts of Syria and Iraq, hinges on Muslims and non-Muslims around the world deciding that there is such a contradiction inherent in their coexistence, forcing them to separate from each other by whatever means necessary.

America has in large part managed to incorporate people from all types of backgrounds in its institutions, many of whom have come to identify with them strongly. The danger of Trump’s candidacy is that it has articulated a popular vision of America that has no place for people like these, whose identities are complex and overlapping. In his world, the very existence of someone like Khizr Khan appears to be a contradiction.

It’s still difficult to imagine such a vision resonating with a majority of voting Americans. But if it does succeed, Trump will have won an achievement that undermines national unity over the long term. There will be less space for people like Khizr, Humayun, and Ghazala Khan, or others who represent a diverse yet coherent vision of the United States. Americans will instead be divided into opposing camps based on their ethnic or religious identity: a catastrophic victory.