Those who cannot learn from history are doomed to repeat it.
Sunder Katwala says we have got to get over Militant and New Labour.
I find this Year Zero approach to Labour history somewhat surprising from the General Secretary of the over-100-years-old Fabian Society.
He quotes a guy in the audience at the "Change we need" event last night shouting out
"I remember the 1980s. The Trots will be back. We must have a Trot infestation strategy".
I suspect it may have been John Spellar, but whoever it was, they were right.
The Bennite left and its Trotskyist allies have not gone away. I see the evidence of that every time I go to my local Labour GC meeting. Their cadres are getting older but a Labour defeat in the General Election will allow them to recruit new activists and reactivate old ones around a myth of leadership betrayal.
Insurgency from the left has afflicted Labour during every major period in opposition - the 1930s, the 1950s and the 1980s.
In every case it has been necessary to wage a long and bitter internal struggle to smash the left and purge entryists who are not democratic socialists in order to make the party electable again.
This is not a pleasant task but it is one that has to be done. Sunder worries that this is "deeply alienating for new generations of activists". Not half as alienating as having your local party taken over by revolutionaries is.
The "why can't we all have a group hug and be idealistic" school-of-thought won't last five minutes once the next big scrap for the soul of the Party starts.
We will need moderate activists with the guts and moral strength to stand up to the ultra left and the stamina to out organise them. If we can get to a position where mass participation means we can just out vote the crazies, as in 1994-1997, then great, but there may well be a period before that when being a Labour activist means entering into a world of pain and political trench warfare, and we shouldn't kid recruits it will all be nice social events and a happy-clappy unified crusade.
Ben Brandzel said at the meeting "When all you have to choose from is professional politicos and the unemployed Trot newspaper-seller, then you are in trouble. Seven loud and angry people can dominate a small meeting".
But we will be in trouble if we lose the next election, and meetings probably will be like that. When that's the choice, those of us who are what Brandzel calls "professional politicos" will have to get eight people of good will into the room to out vote the "seven loud and angry people". Unless you win those fights then the chances of ever getting "thousands of people" involved are nil as the people who actually want Labour to win elections will not control the structures of the party.
The big question that will face Sunder and other people of good will in the party is will they get their hands dirty and help win that battle again or will they be at home watching it on TV and wringing their hands about how nasty it all is.