The United States and Great Britain are suffering through an upsurge of hateful slights and slurs aimed at "others" -- people with dark skin or foreign accents or strange clothes. And there is a clear cause behind the episodes in both countries.

Call it the Trump Brexit Effect.

Politicians on both sides of the Atlantic have given permission for this sort of despicable behavior. They have encouraged and exploited an ancient impulse -- xenophobia, the fear of foreigners -- for cynical political advantage.

Donald Trump says he'll "Make America Great Again," but he really wants his supporters to hear that he'll "Make American White Again." His code words aren't even subtle: build the wall, block the Mexicans, bar the Muslims, boot the immigrants.

In Great Britain, the victorious "Leave" campaigners had their own set of signals. Instead of building walls, they want to demolish the bridges that have connected the U.K. to Europe since the end of World War II.

The message in both places is the same: It's all right to hate. Cut off the world. Keep out the "others." Return to a time when white Christians, especially white Christian men, ran everything.

In describing the Brexit vote to the Huffington Post, Paul Bagguley of the Centre for Ethnicity and Racism Studies at Leeds University could have easily been referring to the Trump campaign, too:

"I think that's given people a sense at which they can express racist ideas and do things they frankly wouldn't do," said Bagguley. "It legitimizes people saying things they might keep private, or just between friends and people they trusted.

"I don't think we've quite seen that before," he added. "I think this is more of a kind of celebratory racism. As if it's in celebration that white England has finally got something."

The latest example of "celebratory racism" here in the U.S. was the Trump campaign tweeting out a red Star of David, layered over a pile of $100 bills and positioned next to a picture of Hillary Clinton, who was labeled "Most Corrupt Candidate Ever!"

The Trumpists insist the image was benign, but they removed it two hours later; investigative reporters traced its origins to "an internet-based movement associated with white nationalism," reported The New York Times.

Erick Erickson, a prominent conservative commentator, skewered Trump's attempts to duck responsibility: "A Star of David, a pile of cash, and suggestions of corruption. Donald Trump again plays to the white supremacists."

The key word is "again." Trump has repeatedly played the race card to stir up supporters, going back to the days when he led the "birther" movement that questioned Barack Obama's credentials to be president. And his vile fear-mongering is filtering down to the playgrounds of America.

Columnist Petula Dvorak in The Washington Post tells the story of Evelyn Momplaisir, mother of a "brown-skinned" third-grader in northern Virginia. "I just got a call from my son's teacher," Momplaisir posted on Facebook in March, "giving me a heads up that two of his classmates decided to point out the 'immigrants' in the class who would be sent 'home' when Trump becomes president. They singled him out and were pointing and laughing at him as one who would have to leave because of the color of his skin."

Similar stories have erupted across Britain since the Brexit vote. The National Police Chiefs Council reports a 57 percent increase in hate crimes. Graffiti scrawled on a Polish community center fulminated, "Leave the EU, no more Polish vermin."

Conservative politician Sayeeda Warsi told Sky News that human rights activists have told her "really disturbing (stories) from people being stopped in the street and saying, 'look, we voted Leave. It's time for you to leave."

"All of a sudden, a small group of extremists feel empowered," Joanna Ciechanowska, an activist in London's large Polish community, told The Guardian. "The margins of society feel they can do it because they think they have the support of half the nation."

Leaders in both countries must show that the haters are wrong. They should follow the example of David Cameron, the outgoing British prime minister, who vigorously denounced the "verbal abuse hurled against individuals because they are members of ethnic minorities."

"Let's remember these people have come here and made wonderful contributions to our country," he said. "We will not stand for hate crimes or these kinds of attacks. They must be stamped out."

Cameron is correct. The Trump Brexit Effect violates our most cherished Anglo-American values. It must be stamped out.

– By Steve and Cokie Roberts, NEA Columnists