Why is it when someone sources Fox News, they're labeled foolish, but when it's CNN or network, it's credible?

This chaps my hide. I will fully admit Fox News certainly leans to the convervative side. I don't think anyone would question that. But why is it when someone sources them, they are labeled as a fool? What if I sourced CNN or ABC News? Then would it be credible? They are just as bad as Fox News for their political leanings. Almost every other major news network is very left wing liberal and no one ever squawks about them! I'm tired of it. The fact is, while conservative yes, Fox News is probably closer to the political center than CNN or just about anyone else is from the left.