This is an American canard, but it's not really true. Usually, public broadcasting reflects the consensus of where the middle is, with a slant towards social justice, almost unavoidable when criticizing public policy - usually stories are about something the government isn't doing, or is doing wrong, rather than shouldn't be doing.

If a public broadcaster publishes plainly biased stories, independent media can lambast them. But the shaming only has effect if the independent media is itself taken seriously; so the critique has to come from the middle ground.

What you won't get from publicly funded news is a rounded perspective on what opposing camps think. The extremes are lopped off; you won't get small government conservative ideology, and you won't get communist ideology. Being anodyne and factual is the best defense against criticism from both independent media and political sources.

If one's own position is significantly to one side of the political spectrum, naturally the middle looks like it's on the other side.