Nice concept... However, if it would come to that, better to have good offense (deterrent) than a "rudimentary" defense. No, this isn't about sports.
We've got a "deterrent" but one which may not in fact deter. In a proliferated environment, deterrence begins to fail. That is why our enemies have in fact been abetting proliferation (E.g., Russia, China, North Korea, and France) with their various proxies, surrogates, such as North Korea...and terrorists...these need to be thwarted with a good defense as well, so that we then have the luxury of sorting out who actually attempted...repeat...attempted to attack us.
Along those lines, you can bet that the NSA, CIA liberals notwithstanding despite their incessant contrary and foolish leaks, concluded that Saddam DID have a hand in 9-11. His posing next to the painting celebrating 9-11 is no accident. We went to great expense and lengths to make things "right" afterwards.
If a nuclear hit on us is successful however, we may not have any way of ascertaining who is responsible. We need defense too.