Now playing
01:01
World leaders react to Brexit
PHOTO: Photo Illustration: Getty Images/CNN
Now playing
03:38
Here's what you need to know about Brexit
Britain
Britain's Prime Minister Theresa May leaves 10 Downing Street in London on March 25, 2019. - British Prime Minister Theresa May chaired a meeting of her cabinet amid reports of an attempted coup by colleagues over her handling of Brexit. (Photo by Isabel Infantes / AFP) (Photo credit should read ISABEL INFANTES/AFP/Getty Images)
PHOTO: ISABEL INFANTES/AFP/Getty Images
Now playing
01:44
Theresa May to resign when Brexit is done
Pro-EU demonstrators wave an mixed EU and Union flag as they protest against Brexit, outside of the Houses of Parliament in central London on June 11, 2018. - After a rollercoaster week of Brexit rows within her government and with Brussels, British Prime Minister Theresa May will on Tuesday seek to avoid another setback in a long-awaited showdown with parliament. MPs in the House of Commons will vote on a string of amendments to a key piece of Brexit legislation that could force the government
Pro-EU demonstrators wave an mixed EU and Union flag as they protest against Brexit, outside of the Houses of Parliament in central London on June 11, 2018. - After a rollercoaster week of Brexit rows within her government and with Brussels, British Prime Minister Theresa May will on Tuesday seek to avoid another setback in a long-awaited showdown with parliament. MPs in the House of Commons will vote on a string of amendments to a key piece of Brexit legislation that could force the government's hand in the negotiations with the European Union. (Photo by Daniel LEAL-OLIVAS / AFP) (Photo credit should read DANIEL LEAL-OLIVAS/AFP/Getty Images)
PHOTO: DANIEL LEAL-OLIVAS/AFP/AFP/Getty Images
Now playing
01:07
What's at stake if a Brexit deal falls through
Pedestrians waling through Waterloo Bridge with the skyline of the City of London in the background on October 27, 2016. 
Britain
Pedestrians waling through Waterloo Bridge with the skyline of the City of London in the background on October 27, 2016. Britain's economy won a double boost on October 27 on news of faster-than-expected growth following its vote for Brexit and a pledge by Nissan to build new car models in the UK. Gross domestic product expanded by 0.5 percent in the third quarter, official data showed. / AFP / Daniel Leal-Olivas (Photo credit should read DANIEL LEAL-OLIVAS/AFP/Getty Images)
PHOTO: DANIEL LEAL-OLIVAS/AFP/Getty Images
Now playing
02:13
Why Brexit uncertainty means companies plan for the worst
PHOTO: Getty Images
Now playing
03:45
What a fish can tell you about Brexit
Cyclists pass a sign calling for no border to be imposed between Ireland and Northern Ireland outside Newry, Northern Ireland, on November 14, 2018 near the Irish border. - British Prime Minister Theresa May defended her anguished divorce deal with the European Union before rowdy lawmakers on Wednesday before  trying to win the backing of her splintered cabinet with the so-called "Irish backstop" arrangement to guard against the imposition of a hard border between Ireland and Northern Ireland one of the contentious issues, according to reports. (Photo by Paul FAITH / AFP)        (Photo credit should read PAUL FAITH/AFP/Getty Images)
Cyclists pass a sign calling for no border to be imposed between Ireland and Northern Ireland outside Newry, Northern Ireland, on November 14, 2018 near the Irish border. - British Prime Minister Theresa May defended her anguished divorce deal with the European Union before rowdy lawmakers on Wednesday before trying to win the backing of her splintered cabinet with the so-called "Irish backstop" arrangement to guard against the imposition of a hard border between Ireland and Northern Ireland one of the contentious issues, according to reports. (Photo by Paul FAITH / AFP) (Photo credit should read PAUL FAITH/AFP/Getty Images)
PHOTO: PAUL FAITH/AFP/AFP/Getty Images
Now playing
02:06
Brexit: What is the Irish backstop?
PHOTO: CNN
Now playing
01:32
Why there is no easy path in the Brexit deal
EU supporters, calling on the government to give Britons a vote on the final Brexit deal, wave EU flags as they participate in the
EU supporters, calling on the government to give Britons a vote on the final Brexit deal, wave EU flags as they participate in the 'People's Vote' march in central London, Britain March 23, 2019. REUTERS/Henry Nicholls
PHOTO: Henry Nicholls/Reuters
Now playing
01:31
Massive crowds march against Brexit in London
Now playing
02:59
May puts the pressure on lawmakers in Brexit address
PHOTO: Parliament TV
Now playing
01:59
Parliament votes to seize control of Brexit process
PHOTO: Parliament TV
Now playing
02:12
Corbyn rips May, demands no confidence vote
PHOTO: parliamentlive.tv
Now playing
01:19
Theresa May's brexit deal suffers historic defeat
PHOTO: EBS
Now playing
02:32
How the EU negotiated its first-ever divorce
PHOTO: CNN
Now playing
01:24
Once pro-leave town feels Brexit uncertainty
Irish border drone footage
Irish border drone footage
PHOTO: CNN
Now playing
01:59
Why the Irish border is impacting Brexit

Story highlights

Britain voting to leave EU is the worst step backward for Europe since the end of World War II, writes Charles Kaiser

Progressive voters must recognize similarities between the Brexit appeals to racism and Trump's attacks on Muslims and Mexicans, Kaiser says

Editor’s Note: Charles Kaiser is the author of “1968 In America,” “The Gay Metropolis” and, most recently, “The Cost of Courage.” The opinions expressed in this commentary are his.

(CNN) —  

The numbing news that Britain has voted to leave the European Union is the worst step backward for Europe – and for Western civilization – since the end of World War II.

There were tens of millions of military and civilian casualties in Europe from that hideous conflict, and it left much of the continent in ruins. But in Europe, World War II also had two extremely positive effects. First, unlike the United States, where there were relatively few casualties at home, the personal experience of the horrors of war by millions of European civilians inoculated their countries against all-out war for the next seven decades.

Charles Kaiser
Charles Kaiser

And, second, within a remarkable group of forward-looking men and women, the end of the war spurred one of the greatest impulses toward unity of all time. These were the visionary politicians like André Boulloche, a hero of the French Resistance, who pushed for the creation of what would eventually become the European Union.

Boulloche paid for his heroism as a Resistance fighter with a year inside three German concentration camps, and the loss of half of his family after they were arrested by the Gestapo, a saga I recount in my recent book “The Cost of Courage.” But like so many other extraordinary European survivors of World War II, Boulloche managed to transform his terrible suffering into a force for good. He became a Socialist politician, the mayor of a small French city near the border with Germany, and a member of the National Assembly.

In a supreme act of intellectual jiu-jitsu, Boulloche took all of the ghastly energy from his wartime incarceration and turned it around to fuel a lifelong devotion to reconciliation between France and Germany. As Socialist leader and future French President François Mitterrand declared at Boulloche’s funeral, “When he turned toward the Germans, he was the first among us who knew how to say, ‘My friends.’”

It was the determination of men and women like Boulloche, throughout Europe, which propelled the movement toward unity. Beginning with the Treaty of Rome, a 1957 modest economic agreement signed by France, West Germany, Italy, Luxembourg, Belgium and the Netherlands, the experiment gradually grew into to the behemoth of a nearly-borderless alliance. It reached its zenith of 28 members with the admission of Croatia in 2013.

Ironically, for many years, it was French President Charles de Gaulle who was the staunchest opponent of expansion of the European Economic Community, because he saw Britain’s entrance as a Trojan horse for the power of the United States. The United Kingdom, Denmark, Ireland, and Norway applied for membership in 1961, but it was only after de Gaulle was long gone from the political scene that Britain was finally admitted.

(The effort of British Prime Minister Harold Wilson to overcome de Gaulle’s opposition was memorialized in a famous 1960s cover of the Economist, featuring dozens of images of Wilson making every imaginable facial expression, paired with multiple images of one indomitable de Gaulle, making the same grimace over and over again. “Keep Right On,” was the magazine’s advice to Wilson, but it was his successor, Edward Heath, who was finally able to push his nation into the European Community in 1973.)

This historic change in Britain’s relationship with the rest of continent seemed to be consolidated for good in 1994, when the tunnel under the English Channel was finally opened, and Queen Elizabeth II traveled on the Eurostar to Calais to inaugurate it with Mitterrand. But nothing is forever when politicians seize on the fear of “the other” – in this case, a surge of immigrants from the Middle East – and use it to promote disastrous policies like Britain’s exit from Europe.

As Felix Salmon wrote at Fusion.net, what happened in Britain was “a wholly unnecessary vote, which was called by Britain’s gormless prime minister, David Cameron, for the sole purpose of trying to engineer a tactical advantage in last year’s general election.” As Salmon also points out, “Northern Ireland voted to remain in the EU; Scotland voted overwhelmingly to remain. England drove this result, and specifically Little England – the older, whiter areas outside the big cities. The Leave campaign might have paid superficial lip service to the idea of a global Britain with more room for Bangladeshi immigrants, but make no mistake: this was a racist campaign that ended up causing both death and disaster.”

Many European diplomats think Britain’s decision must be used to strengthen the community that remains. “These are difficult times,” François Delattre, the French ambassador to the United Nations, told me in an interview, “and we must chase these evil winds of populism by addressing the real issues facing our democracies.”

Peter Wittig, the German ambassador to the United States, echoed his French colleague. “This is a really serious setback,” Wittig told me. “We have to prove to the citizens that the European Union is there for them – that it is a union for the citizens and not a union for the bureaucrats.”

My hope is that the British vote will also have a positive effect on the United States. Progressive voters must recognize all the similarities between the Brexit appeals to racism and Donald Trump’s attacks on Muslims and Mexicans – and then they must mobilize. The Democratic Party must come together in November to make sure that the United States doesn’t take the same disastrous step backward that Britain took Thursday.

Join us on Facebook.com/CNNOpinion.
Read CNNOpinion’s Flipboard magazine.

Charles Kaiser is the author of “1968 In America,” “The Gay Metropolis” and, most recently, “The Cost of Courage.” The opinions expressed in this commentary are his.