Basic problem is, you can't prove a negative.
So the things they did may not work (or, depending on your interpretation, may not work as well as reported.) So? Space-based lasers, ground-based lasers, intercepting missiles, etc. cannot be proven to not work.
I'd rather at least have someone working on the problem than continue to rely on MAD (Mutual Assured Destruction) to protect me from some current or future nuclear-capable country. Sure, that doesn't protect against someone smuggling a bomb into New York's harbor, but the smuggle-bomb, while destructive, is sure as hell going to be less destructive than an all-out ballistic missile attack.