“There was once a need for unions, but they’ve outlived their purpose,” said a nice lady interviewed on the radio in Tennessee just the other day. Annoyed by the spectacle of tens of thousands of teachers, firefighters, cops and other public employees rallying to protect their rights in Wisconsin, she was saying what more than a few Americans think about the labor movement.

They ought to think again — unless they want their children and grandchildren to become the peons of a corporate oligarchy.

Behind the vague notion that unions are somehow obsolete is the suggestion that workers — and their families — are amply protected by the law’s provisions prohibiting child labor and mandating minimum wages, safe working conditions, overtime pay and all the other standards that we now take for granted.

But if you listen carefully to “conservatives” of the ilk of Wisconsin Gov. Scott Walker and billionaire financier David Koch, you’ll learn that they want to do away with most if not all of those advances, hard won by the labor movement and its allies over the past century. Their core belief is that the state should never interfere with capital — and therefore every law defending workers or consumers is a constitutional abomination. Their ultimate project is to return this country to the absolute dominion of the wealthy that existed before the rise of the Progressive Movement and the New Deal.

Politicians like Walker know better than to articulate their goals so unappealingly. Invariably, they prefer to talk about fiscal responsibility and balanced budgets, hoping that nobody will notice (in Wisconsin or Washington) how they squander vast sums on tax breaks for the wealthy while demanding “sacrifice” from the middle class and the poor. Breaking unions is the only way, they tell us, to restore jobs and ensure prosperity.

But if you thumb back through the pages of our economic history over the past hundred years or so, a number of obvious facts stand out. First, the United States enjoyed a far better distribution of income and a steady improvement of our productivity and power when the labor movement was strong. Second, labor always struggled to expand human and civil rights for everyone, whether or not they happened to belong to unions. And third, the success of labor’s effort toward a more equitable society ensured broad prosperity for decades. As labor’s power diminished, income and wealth skewed upward — and helped drive the economy into stagnation and recession.

So Americans not only display ingratitude when they denigrate unions, which have done so much to improve the lives of ordinary people, but ignorance as well. Even in its terribly weakened condition, the labor movement remains a bulwark against the kind of corporate tyranny that would swiftly make serfs of the rest of us.

This week, a prankster pretending to be David Koch phoned Gov. Walker and recorded their chummy, obnoxious, highly revealing conversation. Hearing the governor eagerly agree as his top contributor rambled on about union “bastards” was like listening to a conversation between a robber baron and a servile politician of the Gilded Age. Here was the new version of the unvarnished “conservatism” that ruled us before our forebears learned to stand upright, join together and fight for democracy.

It is more than a funny coincidence that the Wisconsin uprising echoes the revolutionary democratic fervor currently sweeping across North Africa and the Mideast.

Common to every dictatorship, from the fascist and communist despots of the 20th century to their counterparts in today’s authoritarian societies, is the impulse to forbid workers from organizing. The legacy of those who established those rights with their blood and toil, both here and abroad, is not ours to surrender to bullies such as Walker and Koch. Like all of our liberties, it is a trust to be guarded — by every means available.