Great thought experiment from Rich Lowry at Politico:
Imagine if a cadre of journalists were recruited to cover the Obama campaign from 100 devoted Rush Limbaugh listeners living in the 230-mile corridor from Midland to Amarillo, Texas. Imagine they were overwhelmingly traditionalist on hot-button cultural issues and heavily evangelical, owned five firearms each and largely socialized with one another and other conservative Republicans.
They could try their damnedest to be fair to the president whose politics they disdain. Still, their own predilections would inevitably show through.
In the real world, journalists tend to have the opposite of all these qualities, and on top of them are usually self-important and willfully blind to their own biases.