Vice President Biden spoke Wednesday at a memorial service for Sean Collier, the Massachusetts Institute of Technology police officer who authorities say one of the Boston Marathon bombers shot and killed last week:

Biden also used the occasion to deliver a rousing denunciation of the alleged perpetrators who planted the bombs and later murdered Collier, calling them “two twisted, perverted, cowardly knock-off jihadis.”

He said that Islamist terrorists’ “doctrine of hate and oppression ... cannot compete with the values of openness and inclusion” illustrated by the Massachusetts Institute of Technology. “And that’s why they’re losing around the world.... Our very existence makes a lie of their perverted ideology.” Biden added that he was proud the country has not succumbed to the fear that terrorists aim to instill.

Law enforcement officials believe the perpetrators were Tamerlan Tsarnaev, who died in a confrontation with police, and his younger brother Dzhokhar, who is hospitalized and in custody. Investigators believe the two were acting alone:

“These are persons operating inside the United States without a nexus” to an overseas group, a U.S. intelligence official said. Instead, officials said, the evidence suggests that Tsarnaev and his 26-year-old brother, Tamerlan, who was killed during a confrontation with police, were “self-radicalized.”. . .

U.S. officials briefed on the interrogation of Dzhokhar Tsarnaev said he has specifically cited the U.S. war in Iraq and the campaign in Afghanistan as factors motivating him and his brother in the alleged plot.

The young men’s uncle, Ruslan Tsarni, spoke openly and emotionally last week about his nephews. In doing so, argues Asra Nomani, he helped American Muslims to confront the problem of Islamist radicalism:

“Do you think that they got radicalized in the mosques in that area?” I asked.

What I heard I couldn’t believe, I’ve become so used to the tactics of deflection. He looked me straight in the eye, and he said, “…most likely somebody radicalized them. But it’s not my brother, who just moved back to Russia, who spent his life bringing bread to their table, fixing cars, fixing cars.”

What happened when this Muslim American looked us in the eye and admitted the problem?

Tsarni became “Uncle Ruslan” to millions of Americans watching him on TV and later online, winning their respect, first, with apologies and then, with his hands clenched, fierce indignation, outrage and anger over the suspected role of his nephews as the Boston Marathon bombers. (Read the rest of Nomani’s essay here.)

Despite the personal problems Tsarni mentioned, Post opinion writer Ruth Marcus observes that his nephew Dzhokhar seemed normal and untroubled:

See the names and stories of the Boston Marathon victims

Look at Tsarnaev and you see . . . a regular-looking kid, one who — to outside appearances — had, like generations of immigrants before him, assimilated quickly and seamlessly. If he smoked pot, he also volunteered with the Best Buddies program and earned a college scholarship.

He looks like the bad boy in a boy band. His version of wildness: driving his car backward down a one-way street at a prom party — an eerie foreshadowing of the Cambridge, Mass., shootout in which a fleeing Dzhokhar reportedly drove a stolen SUV over his brother, Tamerlan.

“He was just this scrawny little kid who was always giggling and happy,” Juliette Terry, 20, an elementary school friend and part of a group with whom he attended prom, told the Wall Street Journal. “I can’t remember him saying a mean word in his life.” (Read her column here.)