Those who claim that most fact checkers are completely biased, will also claim that most mainstream media is "fake news", that <opposition ideology> is responsible for most social ills, that <person's ideology> is the eternal victim, and so forth.
Recognizing that the truth is not on your political side requires both honesty and clarity of thought, which the average political ideologue is functionally incapable of.
Those who claim that most fact checkers are completely biased, will also claim that most mainstream media is "fake news", that <opposition ideology> is responsible for most social ills, that <person's ideology> is the eternal victim, and so forth.
Recognizing that the truth is not on your political side requires both honesty and clarity of thought, which the average political ideologue is functionally incapable of.