We don't need cosmic deity levels of certainty. Most first-world judicial systems are predicated on the standard of evidence being "reasonable". As in "reasonable cause to believe" or "beyond a reasonable doubt". We have functioned pretty well with based on "reasonable" and we can apply that same standard here. It is fair to label a statement as at least misinformation if it seems to be untrue beyond a reasonable doubt. Disinformation requires intent which is much harder to determine but not really relevant.