Speaking during a memorial service for Sean Collier, the MIT police officer slain by the Tsarnaev brothers last Friday, Biden echoed the question of why anyone would seek terrorise a city.
"Why, whether it's al-Qaeda central out of the FATAs or two twisted, perverted, cowardly, knock-off jihadis here in Boston. Why do they do what they do," he questioned.
Speaking further, he said, "You (audience) are their worst nightmare...All the things, these perverted jihadis, self made or organised, all the things they fear".
"The only way they can gain ground is to instill fear that causes us to jettison our values, way of life, for us to change. The moment we change, the moment we look inward, the moment we get into a crouch in a defensive, that's the moment when they win," Washington Post quoted him as saying.
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"It infuriates them that we refuse to bend, refuse to change, refuse to yield to fear...The doctrine of hate and oppression, they've found out cannot compete with the values of openness and inclusiveness. And that's why they're losing around the world," he said.
"You make no distinction between the competence of male and female. You are their worst nightmare. All the things these perverted jihadis, self-made or organised, all the things they fear," he said.