Let's start with the basics, as we always do and always should.
Unions in the United States at one time had a just and rightful place in the bargaining process between employers and employees - it happened occasionally that employers would overstep their bounds and take actions that would be critically detrimental to the health and well-being of their employees, and unions helped the individual workers from being overrun and run roughshod over. Then a funny thing happened - given that power of bargaining, the unions ran with it, to the ends of the earth. They became institutionalized in certain areas thanks to the Wagner Act, a law designed to step in and force employers to accept bargaining from unions instead of simply hiring a new workforce when their existing one presented "demands" and threatened to walk out. They forced employers to give into almost anything they could come up with, to the point of forcing employers into bankruptcy just to pay for their new "benefits" they were supposedly owed.
Let's get one thing straight right now: the only reason unions obtained any sort of control was the Great Depression. Unions came in and initially were able to help their members keep their jobs - but the employers didn't have the opportunity to just walk away from the bargaining table and find some new workers, because once the unions got their members back to work, they raised the bar for removing people from their positions and made it damn near impossible for employers to remove lazy and unproductive workers from the environment or move more productive workers into new areas. Put simply, unions knocked industry to the ground and sat on it until they got what they wanted, and threatened like that, industry went along to ensure its own immediate or short-term survival.
It gets better. Seeing the control they could obtain over private-sector positions, unions began creeping into the public sector, supposedly to help police, firemen, road workers, secretaries and any other people employed by government at any level. That's led to a number of bad things, like the current fiscal crisis faced by many transit agencies across the country - fares keep going up but service gets cut back further and further because the money has to pay for contracts negotiated by the thugs in these unions.
Let me take a moment here and tell you: both my father and my father in law are involved in unions - my father is a member of the nursing union and my father in law is a member of the railroad worker's union. I won't go further with details because I'd rather not disclose private details, but suffice to say, I've benefitted from union negotiations myself, as the son of a union worker and as the son-in-law of a union worker. That being said, I believe unions should be de-institutionalized, and that all existing union members ought to be able to cast secret ballots determining whether they want to remain as members of the union or to have their workplace union dismantled and removed. The Wagner Act was made for a different time and place, where America was facing different challenges, brought on by socialist policies and heavy-handed government regulation. Pull it out, and let the people decide what they want.
Bring back the free market.