If that were true, why not open the nuclear option to any attack on the US? It would make us safer, no?
Apples and oranges. We've always lumped CBR weapons into the same category as Nukes. They are cheaper, harder to track as far as proliferation, and readily available. They are the ace up the sleeve of a nation incapable of affording a nuclear program, which was why we always treated them the same way. It was an extension of MAD, and it worked. Why the change? How does this increase our security or reduce the likelihood of said weapons' use?
It doesn't.
I fail to see how tying one of our arms behind our back makes us safer. I guess we can feel better about ourselves, right up to the point a state sponsored terrorist unleashes a chemical or biological attack on one of our subway systems.