Luxenberg makes the mistaken assumption, typical of conservative Republicans, that the threat of the Evil Empire can only be contained by military superiority. That assumption is wrong, and therefore turns the rest of his article into nonsense.
Leaving aside the fact that "Star Wars" is in all probability impossible to achieve, or if achieved would almost certainly be negated by well-known countermeasures, let us look at where we actually stand.
The bomb is real and the bomb is here to stay. Even if it is negotiated down to zero-zero level, the bomb is still with us because we can never destroy the knowledge and know how that makes manufacture of the bomb possible.
So why isn't that an argument for having the "Star Wars" umbrella? Simply because the most idealized umbrella can never be leakproof and its development would almost certainly yield, as a byproduct, offensive weapons that may well outclass the bomb in horror.