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.