A brief post via Chris Dillow, then I'm out of here for a bit:
Why are unions unpopular?: ... Nobody under the age of 40 can remember when unions were (plausibly or not) accused of wrecking the economy. Indeed, these days, the wreckers are not unions but managers. From bankers causing recession through bosses plundering their companies to BBC executives stealing licence-payers money, the economic vandals today are bosses, not unions.
What's more, it would be easy to argue that stronger unions would be in everyone's interest, and not just because they help restrain managerial parasitism. They represent the "little platoons" that Tories should admire, and could be part of the "big society" that allows state regulation to be scaled back. And it's quite possible that the higher wages unions want would help the economic recovery by increasing aggregate demand.
Why, then, are unions still seen as the big bogey man...
He goes on to suggest several reasons.