Their own worst enemies
Sometimes there is no need to attack the Hard Left because they do it for you themselves.
Hence the surreal spectacle of a 3-way split in the Socialist Campaign Group of MPs over the coming Labour leadership election - the ultras backing McDonnell, Alan Simpson and others seeking to maximise the left performance rather than just fly the flag by backing Meacher, and a couple of key people like Skinner and Ann Cryer looking like they will vote for Brown.
It's all been recorded in great detail here - http://reclaimlabour.blogspot.com/ and here http://davespartblog.blogspot.com/.
The lack of self-awareness is amazing - why is no one on the left pointing out the obvious - that neither McDonnell nor Meacher is a credible candidate who has any personal base of support in the Party or any qualification to lead it?
It doesn't really matter which of them runs because in both cases they are incapable of reaching out beyond the oppositionalist fringe.
What the squabbling between McDonnell and Meacher exposes is the fundamental crisis of both the Hard Left and the Soft Left in the Labour Party - they are effectively leaderless and have been for some time. The Tribunite tradition threw up some figures of great stature: Bevan, Wilson, Castle, Foot, Kinnock (who came from that tradition even if he didn't stay in it), Cook. With the death of Cook that "soft left" tradition has no leader of national stature or profile, hence Compass et al are attempting to influence Brown, a potential leader from the Atlanticist right of the Party, rather than run their own candidate.
The Hard Left is in even more of a mess - Tony Benn really dominated their emergence as a separate strand of organisation divorced from the old Tribune Group to such an extent that he made everyone around him look like mere acolytes. The more talented of his followers long ago either sold out to become government ministers or, like Diane Abbott, resorted to becoming media pundits or court jesters. The one Campaign Grouper who did have the charisma and appeal to be a credible leader for them - Ken Livingstone - never felt at home in the Commons and was never trusted by his colleagues so has quit the parliamentary stage to go back to running London.
Much as I detest these people's politics I don't think it will be healthy for the Labour Party if they fail to get a leadership candidate on the ballot paper. We need a contested election so that party members get to choose Brown rather than him just emerging, and because a contest will show the public more about Brown's qualities and more about our internal democracy; and we need to have publicly tested and exposed - as by Benn and Heffer's 1988 challenge - how marginal the Hard Left is.
Get your act together comrades!