'Fact checkers' have a credibility problem?

Washington Post:

PolitiFact ventures into Red America on an unusual outreach mission

In West Virginia, the Pulitzer Prize-winning organization's arbiters of what’s accurate meet with those who question their methods of vetting statements uttered by politicians, political organizations and pundits.

I have a low regard for most "fact checkers."  They appear to be an excuse to write a brief for the liberal point of view on a matter in dispute.  They tend to be tendentious arguments to excuse invalid liberal arguments.  It took them forever to attack President Obama's outright lies about Obamacare and this happened after in many cases they had written pieces defending them.  I still do not think I have seen one calling him and Hillary Clinton on their lies about the cause of the Benghazi attacks.  They were willing to go along with a lie that was used to win an election.

It is not unusual for politicians of all parties to say things that turn out not to be true.  Sometimes it is because they don't vet the statements themselves, but when most "fact checks" excuse liberal lies and attack conservative statements that turn out to be suspect they lose credibility.