Luxenberg's thesis--that arms control and "Star Wars" are compatible--is pure pie-in-the-sky. True, strategic defenses would work better at reduced levels of offensive armament but neither side is about to reduce its offensive forces in the face of strategic defenses. To the contrary, the tendency will be to build more missiles to ensure enough "get through."
The second reason given by Luxenberg for his thesis is "the deterrent value of reduced arsenals would be significantly enhanced by the existence of defensive systems." Put in other words, if each side's offensive arsenal were more secure, deterrence would be enhanced. But is this really so in light of the fact with "Star Wars" defenses facing each side, the assurance of "getting through" would be diminished. Each side would account for this uncertainty by building more offensive missiles.
One final note: The ultimate reason why "Star Wars" and arms control are incompatible lies in the fact that "Star Wars" has serious offensive purposes. If battle stations armed with laser or particle beam weapons can destroy missiles in flight, they can certainly destroy missiles in their silos (and many other objects below), which means the side which strikes first can have a substantial preemptive advantage by destroying enemy targets and missiles before they are launched.