The 70s program= Star Wars program?
Or the missile defense plan using land based missles to intercept inbound ICBMs?
In any event, neither was reliable.
A couple of ICBMs may be stopped, the rest will travel to their target... or worse, explode in the atmosphere and rain radioactive material on the world for the next decade.
Do I think they should of stopped development of this? Not at all, eventually they would get atleast 70% reliable.
OTOH, don't believe that these defense systems would of done much more than stopping one nuke safely, while the rest travel to their intended targets or detonate in the atmosphere.
Nukes are nukes, there's no safe way to stop 'em.
-SW