For Labor strategists, the trade union movement has always been the madwoman in the attic. If the unions ever escape their keeper, well, they’ll burn the house down, beat up the guests and prevent Kevin Rudd, the Rochester of Australian politics, consummating his love for the Australian public (“Reader, I voted for him”).

In the past, the Labor argument for silencing the ACTU at national conference time went like this: with John Howard in power and the ALP nowhere in the polls, it would be fatal for the unions to take the spotlight.

In 2009, Kevin Rudd’s in power and the Liberals are nowhere in the polls. And guess what? Unions in the spotlight? Yep, still fatal!

So how does the union leadership challenge this characterisation of itself as an incontinent bedlamite, a more-or-less permanent embarrassment? Well, consider the peace deal struck for this conference, in which the ACTU says it will accept the retention of coercive powers in the building industry, laws that mean workers can be gaoled if they refuse to answer questions. These are extraordinary powers, abolishing the basic common law right of silence in a manner elsewhere seen only in anti-terrorism legislation. If a government imposed similar laws on, say, journalists or politicians, we’d be deafened by the squeals of outrage (one suspects that the building code has been allowed to stand at least in part because of a crude snobbery that holds that rough and tough labourers need careful management).

And what trade-off has the ACTU received for biting its tongue about the building industry? Some encouraging words about its “Buy Australia” campaign! Never mind that it’s far from clear exactly what the government’s agreed to in its procurement plan. Never mind that, in the unlikely event that this minor outbreak of “Aussie Aussie Aussie” protectionism makes any economic difference, it will legitimate an equal and opposite reaction by foreign employers in respect of Australian workers, in the traditional zero-sum game that such things always foster.

What’s more important is what the ACTU’s response to Labor’s conference says about its conception of unionism. As you would expect, the abolition of Howard’s legacy in the construction industry remains a key question for building unions. And, because construction is still so dangerous, the building unions are one of the most vibrant sectors of the movement, capable of mobilising the rank-and-file to a degree that organisers in white-collar industries can only dream of.

Now, with unions everywhere struggling for members and relevance, you might think that blithely abandoning a demand that has regularly pulled thousands of unionists on to the street would be a Very Bad Idea, something calculated to demoralise rank and file stalwarts. After all, the campaign against the building laws has directly involved tens of thousands of people, signing petitions, attending delegates meetings, marching in protest and so on. And it’s that ability to draw ordinary workers into campaigns that distinguishes the unions from any other lobby group. If trade unions can’t involve their members, why would anyone pay them any more attention than, say, the Uniting Church or the Salvation Army or any other well-meaning body that vaguely hopes society might be nicer to the downtrodden?

That’s why a win in the building industry is so important, not just for the CFMEU but for the movement as a whole. Quite simply, it would provide an immediate demonstration of why belonging to a union matters. By contrast, this “Buy Australia” deal has been cooked up by ACTU leaders and Labor ministers with minimal involvement from the membership, and so there’s nothing in it to convince anyone to attend a union meeting.

Of course, if the ACTU did stand firm on construction, it would be immediately denounced as crazy by all the usual suspects. But would that really be so bad? It’s hard to read Jane Eyre these days and conclude that living in an attic worked out so spectacularly well for Bertha Rochester.