So here we have the Gordon Brown, speaking to the 'progressive left' (sic), doing David Cameron's job for him, helping to bolster the tory grassroots by pushing the idea that the Conservatives (in name only) are against the EU, when everyone who knows the recent history can tell you that it was the Conservatives who dragged us into the EEC, as it then was, signed every unifying treaty put in front of them, and has no intention of changing direction on the road to EU superstate hell.
Any thinking conservative has worked out that Cameron is a Blair-style snakeoil monger, but in order for the tories to continue as the major block to real conservative action, they need to keep alive the hope that although they proclaim themselves modern and progressive, at one with the fabian agenda, beneath the superficialities there is a true conservative heart still beating. If they cannot do this, then the true conservatives will finally abandon the tories and find a better vehicle for their aspirations. This is a terrible threat to the status quo.
Meanwhile, labour have to scare their minions with tales of the tory bogeyman hiding under the bed. Only an atavistic hatred for the tories can overcome the sense of betrayal and depression in the hearts of the traditional labour voters.