You said it.
There are two sides to the Second Amendment: One is where the ownership of arms protects your country from a government gone tyrannical. This is a hard sell to those of us who'd never lift a finger against this nation.
The other more agreeable reason for the Second Amendment is to defend your nation against foreign enemies. Though this is a hard sell to people who mock the idea that millions of foreign paratroopers are going to land in our front yards, the real scenario of foreign invaders as shown in the above New York Times article is as legitimate a threat as it gets.
Who will the British sue for not preventing the Islamic takeover of their island, and moreover will Sharia law permit the lawsuit to go forward? Whom will they say should have been aware of the 'warning signs'?
Imagine living there unarmed.