I honestly think that they can not formulate a cohesive counter argument. We’ve had centre-right politics for so long, that it’s become the norm. All three major parties have occupied pretty much the same ground, agreeing over the big issues, but bickering over the minutiae of implementation. This has gone on for so long that it’s become the norm. So when someone with a completely different outlook suddenly becomes the voice of the opposition, and looks as if he’s got ideas that are outside of that small bubble, a panic set in. So this is what is resorted to, and no doubt the press will delight in that assessment of Corbyn. A few headlines will no doubt contain at least one of those accusations.
The Conservatives have a problem themselves. They have a leader who is on the descendent. He won’t be leader in a few years time (you could argue that he’s hobbled himself), and those wanting to take over are already setting out their stalls. So a good, rabble-rousing thrash at the leader of the opposition will ensure that headlines are on Cameron, and not Osbourne, May, Johnson, etc al.