Sybert's statement, "Defensive measures kill no one," is deliberately misleading. A shield is a defensive weapon that enhances the effectiveness of offensive weapons, whether they be spears or missiles.
The SDI is a shield that protects missiles as much as hardened silos do. Defensive weapons are threatening.
And just because the SDI is a "defensive weapon" doesn't mean it can't be defended against. In the last presidential debates, Reagan pointed out that every new weapon eventually had defenses developed against it. In the December, 1981, issue of Scientific American, Kosta Tsipis, a physicist at Massachusetts Institute of Technology, points out the enormous problems with developing the SDI and the ease with which defenses against the SDI can be developed. So the arms race goes on, and the only ones made more secure by the SDI are the defense contractors.