re: "Infallible" defense
On the other hand, if the Maginot Line had never been built, or the wall in China, the walls of Troy, or any other defense, how much safer would those people have been?
Again, nobody has ever assumed such a system would be infallible, but as I've said, a cop is still safer wearing a bulletproof vest even if someone might shoot at his head.
I really don't understand the hostility toward missile defense in general, which seems to be independent of whatever technology is involved. A cynic might conclude that it has a lot more to do with missile defense being associated with a particular political idea set and less to do with any rational analysis of the problem or solutions.