Remember I'm taking the point of devil's advocacy here -- that's what made the Molineux talk so fun. So, taking your points one by one:
dsayers: We live in a world where WMD technology is already out there and widely dispersed, licitly and illicitly -- I'm thinking of the Khan network -- and that bell can't be unrung. In fact I think Stefan's stated view in the above-mentioned talk would have been "I fully support your right to build and stockpile such weapons -- do you support my right to opt out?"
nobody: Governments are indeed the ones with the nukes -- for now -- but that's a causal fallacy. The question before the panel is how to proceed going forward with the technology we're already swimming in.
Will Torbald: Nice. My bet is Stefan would have taken up this line of argument.
shirgall: No line of strategic defense I'm aware of assumes the creation of WMDs from scratch. The usual scenario is a rogue nuclear or biological researcher stealing material from a laboratory. But even if you discount this highly plausible scenario, the enrichment of uranium is time-consuming but incredibly low-tech: If you can build a clothes-dryer you can build a cyclotron. Existing weapons-grade biological agents are even easier to replicate on a massive scale.
dsayers: To my earlier point, that just ain't so -- the tech is within the capability of any •undergraduate• physics or bio major with access to the materials -- I know this from a wee bit of personal exposure -- and, a statist would say, only the leviathan of government is equipped to meet the threat of weapons that, block by block and square mile by square mile, would violate the non-aggression principle in such a vast and cataclysmic way.
Again I say all this from a point of devil's advocacy. I welcome and hope for a good refutation.