In 1949, the British colonial authorities who ruled Kenya became clenched with fear of a popular uprising, and began a years-long wave of arrests that would eventually become one of the worst episodes of the colonial era. One of the men they swept up was a 50-something cook named Hussein Onyango Obama.

Obama was an unlikely candidate for the arrests. He had dedicated much of his life to working with the British, joining the King's African Rifles to fight for the empire in both world wars. In peacetime, he worked as a cook for British families in Kenya. And he was a member of Kenya's Luo ethnic group, whereas the nascent uprising was led mostly by members of the Kikuyu.

But this was not a rational time in British-ruled Kenya. Colonial authorities would ultimately herd at least 80,000 into concentration camps that became, as Harvard historian Catherine Elkins described them, "Britain's gulags."

The camps industrialized torture, most infamously using pliers to castrate large numbers of Kenyan men, and killed as many as 25,000. It was all to put down an insurgency, known as the Mau Mau Uprising, that killed only 32 colonists.

Hussein Onyango Obama survived the British camps, but his family has said he described a daily routine of horrifying and at times sexualized torture, including having his testicles squeezed by metal rods, and that he was never the same again.

The reason we know Hussein Onyango Obama's story is that, decades later, his grandson, Barack Hussein Obama, would become president of the United States. Hussein Onyango Obama's wife was still alive, and gave interview after interview to often-British reporters who wondered, as a 2008 Guardian article put it, whether "Britain's colonial sins pose a risk to our relationship with the soon-to-be most powerful person on Earth."

Almost no one asks this anymore. Partly this is because, after seven years of Obama's presidency, the answer is demonstrably "no." The American-British special relationship has remained status quo, and while Obama is known for at times criticizing allies, he seems more inclined to do so toward Middle Eastern allies, and his criticism of European allies tends more toward the French.

But this is also because it has been deemed unacceptably offensive, even racist, to ask whether Obama's view of the United Kingdom could be affected by the fact that this nation wrongfully tortured his grandfather as part of a systematic campaign of violence that this nation was covering up for most of the president's life.

Nigel Farage, for example, the leader of the hard-right British political party UKIP, drew trans-Atlantic outrage for telling the BBC this week, "because of his grandfather and Kenya and colonisation, I think Obama bears a bit of a grudge against this country." So did right-wing London Mayor Boris Johnson, for a column musing on "the part-Kenyan President’s ancestral dislike of the British empire."

And, indeed, when Obama is accused of bearing an "anti-colonial" grudge, it is typically framed as irrational, often implied to be racial, or made alongside an accusation that he secretly hates America. "Anti-colonial" has become a kind of dog-whistle, and at times a racist one.

Why? Why is this possibility — that Obama might mind that his grandfather was wrongly and unapologetically tortured — so taboo that it is raised only as part of an often-racist dog-whistle?

In this way, one is reminded of the long-running, and false, accusations that Obama is secretly Muslim. And one is also reminded of former Secretary of State Colin Powell's famous quote, "The correct answer is, he is not a Muslim, he's a Christian. He's always been a Christian. But the really right answer is, so what if he is?"

There is no evidence whatsoever that President Obama bears a grudge against the United Kingdom over that country torturing his grandfather as part of a systemic campaign of violence that the UK still refuses to fully confront.

But so what if he did? Would that really be so shocking or unreasonable that we would treat it as taboo to even consider it a possibility?

President Obama is not the first head of state to do business with countries that mistreated his ancestors. But, frequently, it is assumed that those heads of state will bring that history with them — and that doing so is acceptable, even appropriate.

Former Polish President Lech Kaczynski and his brother, former Prime Minister Jaroslaw Kaczynski, often spoke of their father's role in the 1944 Warsaw Uprising against Nazi rule, which biographers tend to describe — always in positive terms — as formative for how they led Poland.

This is common for eastern European leaders, whose leadership we assume will be heavily influenced by memories of how Nazi or Soviet occupiers treated their ancestors. And we extend this thinking, with good reason, to the rest of Europe.

Consider, for example, this detail from a 2014 New Yorker profile of German Chancellor Angela Merkel, on historical grievances that hang over Germany's relationship with Russia:

In 1999, [German Culture Minister Michael] Naumann, at that time the culture minister under Schröder, tried to negotiate the return of five million artifacts taken out of East Germany by the Russians after the Second World War. During the negotiations, he and his Russian counterpart, Nikolai Gubenko, shared their stories. Naumann, who was born in 1941, lost his father a year later, at the Battle of Stalingrad. Gubenko was also born in 1941, and his father was also killed in action. Five months later, Gubenko’s mother was hanged by the Germans. "Checkmate," the Russian told the German. Both men cried. "There was nothing to negotiate," Naumann recalled. "He said, ‘We will not give anything back, as long as I live.’ "

We tend to consider it not only legitimate but to some degree noble that European leaders might carry on the memories of their ancestors' suffering, and might seek redress for historical wrongs.

But this right is rarely extended to the victims of colonialism or their ancestors. While there are exceptions — we often accord Vietnamese leaders, for example, legitimacy in raising French or American abuses in their country — they are rarest of all when it comes to sub-Saharan Africa.

The causes of this are likely more complex than a racial double standard, even if that is the ultimate result.

Post-colonial nations, for example, often rely on their former overlords for foreign aid or other forms of support, forcing leaders to put aside historical grievances. And governing elites in post-colonial countries frequently consist of families who were also part of the local elite during the colonial era. That does not necessarily mean their ancestors were collaborators, but it does mean they were less likely to suffer the worst abuses.

Even in nations such as Algeria or India, where independence fighters dominated post-colonial governments, leaders are typically more concerned with working alongside their former colonial masters than they are with pressing historical grievances.

All of this has created a norm whereby we assume that European leaders will and maybe should use their office to press historical grievances on behalf of their families and by extension their nations, but non-European leaders, and especially sub-Saharan African leaders, will and should not.

President Obama, obviously, is an unusual case. He is the leader of a Western nation that, while a former colony, is far enough beyond its colonial legacy that no one really expects an American leader to seek redress for his or her great-great-grandfather's mistreatment by British redcoats.

But Obama is still also the grandson of a Kenyan citizen who was wrongly imprisoned and tortured by a foreign government with which he regularly interacts. While Obama has chosen not to bring this up as president, it is striking how fully we have internalized the idea that it is taboo to even suggest that Obama could bring it up.

Clearly, this is somewhat particular to Obama and to specifically American racial issues. Whereas Marco Rubio and Ted Cruz can proudly tout their family's migrant histories, Obama has learned that he cannot. Even acknowledging his own race, much less his family connection to Kenya, is a political liability.

This is obviously not the case in other post-colonial countries; it's not as if Liberian racial politics prevent President Ellen Johnson Sirleaf from acknowledging that she is black.

Still, while we can admit that the difficult realities of racial politics prevent Obama from raising his family's history in Kenya, we do not need to assume that it is impossible for Obama to raise this in good faith.

We do not, after all, consider it taboo to suggest that Obama's racial identity might affect how he thinks and talks about, say, police violence against black American communities. Indeed, we rightly credit him as uniquely insightful because of this, even if Obama also faces greater scrutiny on fairness toward police as a result.

But, when it comes to Obama's grandfather and the crimes he suffered at British hands, we have so fully internalized this topic as taboo that it is now the redoubt only of racial or outright racist dog-whistles.

This taboo speaks to the global double standard that discourages redressing historical grievances when those grievances are colonial. And it's a shame, because this is a history that could stand to be exorcised for the benefit of both the Kenyan and British people.

What British authorities in Kenya did to Hussein Onyango Obama, they did to tens of thousands more, or worse. A number of survivors and probably some colonists are still alive. This is a history that is still unreconciled, in both the UK and in Kenya.

Obama himself frequently discusses the wounds and burdens of history, and in other countries and other contexts has worked to address and thus perhaps help heal those histories.

In the case of the UK and Kenya, he is part of that history himself, making him, it would seem, ideally suited for it. While political realities make that impossible, it is worth acknowledging those realities for what they are, rather than allowing ourselves to perpetuate the taboo of colonial grievance.