What Sean's position here amounts to is a recipe for perpetual inertia. For never doing anything, ever. When will the time come for the unions to finally make a break? How long is Sean prepared to wait for the "openings" in the Labour Party to emerge?
I don't deny that such "openings" are a possibility. But acknowledging the possibility and basing your immediate activist orientation on it are two very different things. Because of the long process of destruction of the potential channels of democracy in the Labour Party (culminating in the Bournemouth conference changes), and the entirely legitimate and incredibly widespread bitter hostility to the Labour Party by most politically minded working-class people, the likelihood of the sort of revival Sean imagines is extraordinarily remote.
I'd like to know concretely how Sean imagines this revival taking place and where the people rushing into the Labour Party to carry it out are going to come from. I don't know if he's been to a CLP meeting recently but the picture is not pretty; for a thing to "revive", it needs in the first place to be, well... not dead. And the CLPs are dead. In 2006, I went to a meeting of an Islington CLP that I was reliably informed to be one of the most left-wing and active in the country (in Jeremy Corbyn's constituency, no less). There were less than 12 people at the meeting and apart from one of the platform speakers, I was the youngest person by at least 30 years. And that's the best-case scenario. That is not something that's going to "revive" almost spontaneously just because Labour are forced back into opposition. If anything, I think the opposite is more likely - despair will increase, and the tiny, dwindling number of decent people still left in the Labour Party will drift away.
And against the backdrop of all of that, Sean wants us to oppose a historically militant and at least semi-political union (the CWU) making a clean and concerted break with the New Labour machine and rather pin its hopes on something that a) might not happen, b) it has no real power to make happen and c) even if it does happen, may take years. It is inconceivable that the kind of openings Sean talks about could ever have happened without a significant process of self-assertion by the union within the Labour Party - a coordinated campaign of resistance to the Bournemouth changes, for example, might've forced open some space. But no such resistance took place (quite the opposite, in fact), and now the channels the unions might've used to force such openings have either been concreted over or simply done away with.
The New Labour leadership in opposition might dress itself in vaguely social democratic looking clothes to counterpose itself to an aggressively right-wing Tory government, but that is not the same as an "opening" for us. The New Labour leadership is not going to voluntarily return the party to the sorts of structures that in the past allowed for socialist and working-class struggle within it, and the means by which it might have been forced to are now, as I say, precluded.
This is all to say nothing, of course, of the fact that it is CWU policy that it will disaffiliate if Labour privatises the Royal Mail, which is it in the process of doing. Don't we want to hold the CWU leadership to account on that policy? Not only should we be generally in favour of disaffiliation as a perspective, but in unions like the CWU where it is posed as an immediate question we should initiate the move and fight for it ourselves as a matter of priority, or else risk being outflanked by either the Socialist Party or right-wingers who have an apolitical or anti-political conception of disaffiliation. Clearly, our lack of implantation in the CWU may prevent us from being able to carry this out practically but as a perspective I think it still holds.
The Labour Party has shuffled off this mortal coil, Sean. It is not resting. It is not pining for the fjords. And it is not the business of revolutionaries to tell worker-militants, rightly disgusted beyond the point of all toleration with the actions of the Labour Party, that their unions must continue to pay huge sums of money for the privilege of being shackled to its corpse on the off-chance that, sometime in the indeterminate future, someone might discover a method for raising the dead.