Sounds like the Liberals are scared because they might get a taste of their own medicine.
Historically that 'medicine' has been administered by conservatives. A little thing called 'McCarthyism' comes to mind. Or the regular practice of black-listing potential employees if they are seen to be too active in trade unionism (the amusingly-misnamed "Freedom Association" here used to maintain a database for employers to consult for that specific purpose - when the data protection act meant they couldn't legally keep such records in computer form, I heard they got round it by switching to using a card index).
The distinguishing characteristic of liberals (which sometimes makes them annoying to leftists) is their emphasis on 'diversity' of views. That's why the Gaurdian, though essentially a centrist, paper, is one of the few parts of the mainstream media that carries opinion pieces by actual leftists on occasion.
For the same reason the Guardian has carried articles by Tea-Party supporters and other conservatives (as if they don't already have plenty of platforms available to them). It's Liberal, i.e. it makes a big thing out of 'diversity of opinion'. That's what liberals do, unlike conservatives (or, to be honest, the left).