You seem to confusing not ruling someone else's claim impossible, with personally making a claim something is possible.
Huxley was a scientist, who defined agnosticism as faith in the scientific method, and described it as a form of demarcation. No objective testable evidence = a subjective unfalsifiable claim. Results: unscientific and inconclusive. No belief as to the truth, or falsehood, of the claim.
If you think there is falsifiable evidence you can show is false, then you're making a counter-claim, and it's up to you to present your evidence to back up your claim.
An analogy to consider, though: No matter how many sci-fi stories (Dune, Superman, E.T., etc.) you can show are fiction, you'll still not have actually addressed the existence, or non-existence, of "aliens".
For the very reason a Bible isn't valid testable evidence for the existence of "gods", it isn't valid testable evidence for the non-existence of "gods".
While I'm on board with telling someone a Superman comic isn't valid evidence "aliens" exist, you'll lose me if you claim it's valid evidence "aliens" don't exist.