A fact can be verified. Someone with the necessary knowledge to verify a fact is a fact checker in that particular domain of facts. They are not infallible though, let alone unbiased; even though the facts themselves are immutable and, well, factual.

That said I agree wholeheartedly with your assessment on critical thought. It should be everyone's duty to verify facts for themselves but... consider how many people are functionally illiterate in the world. They wouldn't be able to verify even simple facts, because they lack the mental framework to do so (i.e. reading comprehension). And also consider how much of a burden it is to individually verify every single claim that is made, and compare it to how easy it is to make wild claims. It would be impossible to navigate the modern world without a group of dedicated fact checkers that you trust. You can't be an expert on everything -- and if you think you are, that means precisely that you are NOT.