>>The "proof" of a theory depends on its usefulness in predicting the future. But, a response can only be judged "incredibly stupid" with the benefit of hindsight.

That's true for empirically demonstrable theories,
But some things or actions can be judged to be "incredibly stupid" a priori.

For example:
Repeatedly performing action X and repeatedly getting result Y and then performing action X and expecting a result that is not equal to Y is pretty stupid, period.