White hot fury of a hundred suns referred to, well, a hundred missiles hitting a ship, not whats needed to cause one point of damage. :p
Missiles arn't absorbing damage. Even if you mount armor on a missile, that just gives you a chance of surviving a blast - it doesn't actually sublimate energy harmlessly the way ship armor does. In otherwords a missile is exactly as tough as any ship subsystem - it breaks when you poke it. I like to think of it as any 'hit' being the explosion close enough for a size one explosion to irradiate or otherwise cripple/destroy the missile; armor just means the hit needs to be closer or stronger, thus the % chance. In this scheme, a warhead less than 1 damage-point just isn't practical in terms of the range an AMM needs to detonate at to destroy an incoming missile.