Aucbvax.1495
fa.arms-d
utzoo!duke!decvax!ucbvax!dlw@MIT-AI
Tue Jun  2 22:52:56 1981

I have seen this claim before (that MIRV makes first-strike make more
sense because you no longer need one silo to knock out another silo).
As far as I know, this is generally accepted as true, and you can read
it in books on nuclear deterrence.  (I am not totally certain about this.)