It seems to me that being fact-oriented, especially when preferring facts from authorities and institutions, tends to get a source labeled as liberal-biased.
The trouble is that even if these facts are unambiguously correct, their reporting can be misleading, by interpretation, implication, conjecture, selective reporting, and/or omission. That's how bias is injected even into "factual" reporting, and why reality's "liberal bias" may just be a reflection of the predominant institutional bias in popular media.
