While liberals may sometimes be biased towards conclusions that support their beliefs, this does not necessarily invalidate those beliefs; one would naturally also appear biased towards conclusions that were overwhelmingly supported by evidence. The claim of "liberal bias", then, while it may be true sometimes, is often used as an argument from subjectivity – a politically-tinted version of the "That's your bias" argument, and a way to avoid losing an argument against conclusions that happen to support liberal policy without actually countering them.
Anti-liberals – typically conservatives of one stripe or another – tend to be oriented towards perception-based thinking, so what they really mean by an accusation "liberal bias" is "you're going off-script" – you're not staying within the narrative they're trying to establish.
This also means that:
- If you try to interrogate their position in order to clarify it or understand its relationship to other things, you're implicitly disputing the idea that the dominant narrative defines the truth. (This tends to make them angry, although they often don't seem to understand why.)
- If you don't promptly concede to their narrative, then you're more or less declaring yourself an enemy.
- An accusation of liberal bias is implicit in the more specific phrase "liberal media bias".
- "That's your bias."
- Wikipedia redirects to media bias as of 2015-01-25
- Conservapedia: "partisan selection or distortion of information to support liberal policies. This bias can be expressed by professors and public school teachers, College Board exams, reporters and other journalists in mainstream media, and any other information source."