...There's another possible explanation behind FactCheck's positions. Just last year, FactCheck's primary funding source, the Annenberg Foundation, also gave $50,000 to the Brady Center to Prevent Gun Violence for "efforts to reduce gun violence by educating the public and by enacting and enforcing regulations governing the gun industry." Annenberg made a similar grant for $100,000 in 2005.
Oops. Factcheck tries to defend themselves in that Annenberg also donated to several Republican organizations not realizing that Brady was a Republican. That still has nothing to do w/ financially supporting an anti-gun organization though while trying to claim impartiality on an issue.
Here's the author on his feelings about the NRA:
“They are lying. This is what they do. This is how they make their money. Do these people have no shame? They are just making this up. I just wish that they would tell the truth.” He said that their ads were “one of the worst examples of lying” that he had “ever seen.”
"this is what they do".
So he has a preconceived opinion while claiming to be impartial.
More here, here,here, and here.