Kirsty Wigglesworth / AP

Asked whether his temporary ban on Muslims entering the United States would apply to London’s newly elected mayor, Sadiq Khan, Donald Trump responded, “There will always be exceptions.” (Trump has justified the ban by arguing that the United States doesn’t have a competent border-screening system. His screening system, evidently, is personal whim.)

With his statement, Trump invited Khan to betray his fellow Muslims. Like the anti-Semitic princes who offered special protections to “Court Jews” or the plantation owners who treated house slaves a bit less brutally, Trump offered Khan a dispensation. Had Khan taken it, Trump would have made him complicit in a system of bigotry and oppression.

But Khan refused. In so doing, he followed a classical model of heroism. From Moses, who grew up in Pharaoh’s palace but risked his life to save a Jewish slave, to Nelson Mandela, who repeatedly spurned the South African government’s conditional offers of freedom, Khan placed moral solidarity above personal benefit. “This isn’t just about me,” he explained. “It’s about my friends, my family, and everyone who comes from a background similar to mine, anywhere in the world.”

Notice what Khan didn’t say. He didn’t say he refused to be an exception because he’s Muslim. He said he refused to be an exception out of solidarity with “my friends, my family, and everyone who comes from a background similar to mine.” There’s a crucial difference. You don’t have to be Muslim to have Muslim friends and family. You don’t have to be Muslim to come from “a background similar” to Muslims. All of which raises a question: If Khan won’t make himself complicit in Trump’s Muslim ban, why should any foreign leaders who aren’t Muslim make themselves complicit? If he won’t come to an America that imposes a religious test for entry, why should they?

Imagine if hundreds or thousands of non-Muslim mayors, heads of state, and celebrities from around the world publicly followed Khan’s lead and said that they too won’t take advantage of their privileged status. Or imagine if they vowed to come to Trump’s America and tell border security that they are Muslim. Such a movement might help Americans realize how repulsive non-Americans consider Trump’s Muslim ban. It might help them realize how catastrophic any effort to implement it would be. According to a poll in March, 50 percent of Americans support the ban. A global movement of non-complicity might bring that number down.

And even if it didn’t, it would be an important symbol in this era of religious hatred. Last December, al-Shabab terrorists demanded to know the religion of the travelers on a Kenyan bus so they could slaughter the Christians. The Muslim passengers refused, and thus inspired people across the globe. King Christian X of Denmark remains famous for supposedly telling the Nazis that if they made his country’s Jews wear the Yellow Star, he would wear it, too. The story is almost certainly apocryphal. But its longevity testifies to the power of the idea that, in moments of crisis, people will risk their own safety to protect the vulnerable, even when the vulnerable don’t look, dress, or pray like them.

Trump’s impending nomination creates such a crisis. Khan offers a model for how to respond.

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