I don’t understand why this is being downvoted. I was literally told this by multiple people. Hell, even I have this feeling. I’m not even american and I know fact checking is done by liberals for liberals.
Online user-generated-content moderation systems (whether upvoting/downvoting, Slashdot-style, etc.) are just a type of "fact-checking" in practice.
When the ability/opportunity to act as a moderator within such a system depends on conforming with the community, then biases can become repeatedly amplified over time, and the results of such moderation become questionable to a sizable part of the population.