I believe that a flying unicorn orbits the moon. When no unicorn is found, does that prove that a unicorn may exist?
You can't use a negative to prove a point. Either the point is proven and supported by evidence or it is just speculation. If it is speculation, then it can be dismissed since it has no basis in reality.
In this particular case, if an audit was done and found no backdoors then as far as we know and until such a time as we find a backdoor, then there are no backdoors.
If you want to continue to believe that there is a backdoor, then this is an opinion which does not constitute proof of any sort and certainly should not be used to come up with policies such as banning a company from operating in the US in case of a mythical backdoor which has so far eluded everyone.
Russell’s teapot is not a logical proposition as to what’s true and what is not. It is philosophizing about burden of proof in a low information context in a debate. It is a persuasion tactic, an exercise in philosophy, not at all a logical proposition.
Also its context (religious belief in a deity) is not at all like a scenario where a history of adversarial motives are established. There would be reason to believe the adversary would do certain things if they could, simply because the incentive is so strong and their history of behavior suggests that.
Simply the line that was suggested “there is no backdoor until we find one” is logically self-defeating. The logical proposition of the existence of backdoor cannot be a function of us finding one or not. You can discuss what the policy should be as a risk analysis question, not as a logical “there is no backdoor” from Iraqi Information Officer meme template.
