Comment by naasking

"Unbiased" would be a complete and detailed recitation of all of the facts surrounding an incident, arguably down to particles. Anything less introduces some kind of bias. For instance, describing an event as an interaction of people, omitting particles/field details, introduces human bias. That's a natural and useful bias we don't typically care about but does come into play in science.

Political bias creeps in when even the human description of events omits facts that are inconvenient or that people consider irrelevant due to their political commitments.