Your example appears to be similar to my example of the tap water: In a case of a threat but without proof, we may make a decision that will help us be safe.
Otherwise, in a case without threat, we are reluctant to devote the resources to develop a proof and just ignore the claim that has no proof.
Yeah, but what's a proof? What if Putin try to poison Navalny (as he did), but will deny it? Everybody believes that, but there is no proof that he is in charge.
Does it mean that this is misinformation until proven otherwise, and Russian censorship is justified?