Why does the BBC so love lefty journalists?

My response to the appointment of Ian Katz, deputy editor of the Guardian, to the editorship of BBC2’s Newsnight has been one of disbelief and amusement. Of course there’s nothing new in the Beeb hiring a paid-up Guardian-ista. It’s what we have come to expect. But one might have expected its new director-general, Tony Hall, to tread a little more carefully.