There is no such thing as impartial news any more than there is impartial history.
We are humans, and every last one of us has biases, some of which are quite unconscious. They arise from such things as our upbringing, our life experience, our nationality and the books we have read (if any). That's quite apart from the nutters who believe every conspiracy theory they read is 100% fact.
I honestly think the best thing would be to have a large sub-title under each speaker (including the interviewer or chairperson) saying 'Tory', 'Labour', 'Spume flecked Brexit crazy', 'Commie', or whatever.
I am good at picking up political bias as it was part of my training at college/uni and because my mind works that way. Most people don't have that. They tend to think anyone they disagree with is 'biased' or a 'leftie'. It's spurious bollocks.
(By the way, a common failing is to believe the world splits into ordinary, common-sense people like what I am who aren't political and lefties. This is spurious bollocks too.)