“The price of freedom is eternal vigilance.”
It would be wonderful if defending freedom were a one-off job like proving Fermat’s Last Theorem. As it turns out, it’s an endlessly recurring job like fighting disease; unfortunate, but that’s the way it is. And yes, sometimes our efforts fail, and freedoms are lost or people get sick and die. But the answer to that is to work harder and smarter, not to give up.
Testing rationality is something of an ill posed problem, in part because the result depends greatly on context. People spout all kinds of nonsense in a social context where it’s just words, but usually manage to compartmentalize the nonsense in a material context where they will be affected by the results of their actions. (This is a feature! Given that evolution wasn’t able to come up with minds that infallibly distinguish true beliefs from false ones, it’s good that at least it came up with a way to reduce the harm from false beliefs.) I’m not sure how to create an accurate test in the face of that.
Your martial arts analogy isn’t a bad one. The outcome of a karate contest is often not the same as the outcome of a street fight between the same participants. There are any number of cases of a black belt karateka with ten years training getting into a fight with a scrawny untrained criminal, and getting his ass kicked in three seconds flat. Martial arts practitioners have had this testing problem for centuries and still don’t seem close to solving it, which doesn’t make for optimism about our prospects of solving the rationality testing problem this century. Given that, proceeding as best we can in the absence of a comprehensive and accurate test seems reasonable.