See, this is the rub. If I ask you why you consider factcheck.org more biased than any other site, I won't have any better way to verify the credibility of your evidence than I do to verify the credibility of factcheck.org directly. It wins us nothing but uncertainty!
Does anyone have a good algorithm for this problem that does not degenerate at some point to blind faith in some ideology?
One method would be bypassing intermediate sources like those at issue where the direct source (i.e., the FBI report) is available.