According to a relative of Tamerlan Tsarnaev, the Chechen immigrant believed there is “oppression of the Muslim population around the world.” The relative described Tsarnaev to The New York Times this way: “He was angry that the world pictures Islam as a violent religion.”

Bombing the Boston Marathon was the Tsarnaev brothers’ way of defending Islam. To say their argument boomeranged, however, isn’t fully true. Not as long as the Obama administration puts religious blinders on the defenders of our homeland.

At its core, the Boston case reveals two fundamental truths. One, not all Muslims are terrorists. Two, in recent times, almost all terrorists are Muslims.

Willie Sutton robbed banks because that’s where the money is. Police didn’t catch him by staking out lemonade stands.

By the same logic, preventing terrorism requires close scrutiny of Muslim men leaning toward violent jihad. Had they followed that logic, the FBI could have prevented the bombing.

But with each passing day, it becomes maddeningly clear that political correctness was complicit in the failure. President Obama’s stubborn refusal to connect the dots to Islam isn’t just a personal tic. It reflects the policy he has spread throughout the bureaucracy, including law enforcement and the military.

At the least, orders to “see no Islam evil” created extra hurdles for those trying to keep America safe. At the worst, they opened the door to the bombers.

The moral of the story is that political correctness kills.

We already knew that from the shooting at Fort Hood, Texas, where 13 service members allegedly were murdered by Maj. Nidal Malik Hasan. Witnesses say he shouted, “God is great,” in Arabic as he started a massacre that also left 30 other people injured.

Although Army brass and anti-terror officials knew Hasan, a psychiatrist, was a radicalized Islamist, they took no action for fear of violating his rights. His colleagues called him belligerent, paranoid and schizoid, but he was promoted. When Hasan communicated about suicide bombings with Anwar al-Awlaki, an American-born terror leader living in Yemen, his superiors remained silent.

All this happened when George W. Bush was in the White House.

After Hasan allegedly turned Fort Hood into a bloodbath in November 2009, the Obama administration termed the shooting “workplace violence” instead of a terrorism, an outrageous designation that remains in place. In a remark that still takes the breath away, the Army chief of staff, Gen. George Casey Jr., declared that, “as horrific as this tragedy was, if our diversity becomes a casualty, I think that’s worse.”

The US later droned Awlaki, making for a curious double standard. If he was worthy of death, wasn’t Hasan at least worthy of scrutiny?

Which brings us back to Boston. In March 2011, Russian officials warned the FBI that Tamerlan Tsarnaev was “a follower of radical Islam” who had “changed drastically since 2010.” They also knew he was planning a trip to a hotbed of terror in Russia.

That’s an incredible amount of detail. The FBI has said many things in its defense, some conflicting, but closed the case because agents found no evidence of terrorism or a crime.

That’s a non sequitur. The Russians didn’t accuse Tsarnaev of committing a crime; they said he was a radical Islamist. Why did the FBI limit its concern to actual crimes?

The emerging reason is that bureau guidelines eliminate Islam and other religions as a red flag. In this case, making an actual crime the threshold meant Tsarnaev’s links to radical Islam were ignored or downplayed.

Blinders in place, the screw-up continued. The frustrated Russians gave the same warning to the CIA six months later and added Tsarnaev’s mother was also a threat. Again nothing was done, except both were put on a list with 700,000 other people. He went to Russia in 2012 and stayed for six months.

If the Russians were so clueless, how did they know his travel plans a year in advance? And The Washington Post reports that a source warned the Joint Terrorism Task Force that, after Tsarnaev returned to the United States, he had become radicalized — but still nothing happened.

After all that, the FBI continues to defend its conduct, with an official telling The Washington Post that “since there was no derogatory information, there was no reason to suggest that additional action was warranted.”

This is worse than scary — it is nuts. By definition, the information about Tsarnaev was “derogatory.” It was also true.

The Russians knew he was dangerous two years ago. The FBI figured it out only after the bombs went off.

There’s no stopping the city $pin machine

Thanks to the latest money-burning idea from the city’s Department of Transportation, New Yorkers have a clear view of government gone wild. Asked by The Post how much it costs taxpayers to have workers stand in bicycle lanes holding stop signs and instructing riders how to follow the law — duh! — the department refused to answer. But a spokesman insisted that using city workers saves “costs associated with contracting out” the sign-holding services.

Let’s unpack that stinking load of bull. First, the Bloomberg administration outsources many jobs because it saves money, so somebody at City Hall ought to, in the 12th year of the administration, bring the transit hacks up to snuff.

Second, comparison pricing wasn’t the point of the question — it was whether the job needed to be done at all. But New Yorkers have a better chance of getting hit by a zombie biker than getting the truth out of the DOT.

The agency has fudged statistics for years to justify its policies. From the impact of pedestrian plazas on traffic speeds to accidents involving bikes, to the number of two-wheeled commuters, the agency gives spin a bad name. When facts don’t fit, a lie will do just fine.

Meanwhile, roads are congested and rutted and street lights on highways are optional. Yet workers, one of whom told The Post he earns $50,000 a year, stand around holding stop signs, a job that went the way of the dodo birds a century ago.

Apparently honesty and common sense are extinct, too.

Taxpayers stuck with big fat bill

Alarmed about obesity, Mayor Bloomberg wanted to block the use of food stamps to buy sugary drinks. The feds said no, so he tried to ban sodas larger than 16 ounces. A judge said no.

Now comes word that diabetes, often linked to obesity, drives up health-insurance prices by 10 percent.

As for settling the tab, maybe taxpayers should say no.

Odd prez out at Dubya’s party

Beyond the feel-good moments, the opening of the George W. Bush library and museum provides two takeaways. Barack Obama and Bush now have the same approval rating, 47 percent. And, to judge from body language and the distance they kept, nobody likes Jimmy Carter.

Do you blame them?

Liberally defined

“DC, stars toast ‘Diversity in Media,’ ” read a Politico headline about a reception before the White House Correspondents’ Dinner. It turns out white liberals, black liberals, Latino liberals, Asian liberals and gay liberals gathered to hear praise of President Obama. That’s diversity, media style.