When one criticizes public service unions this doesn't imply at all that one is critical of labor unions per se. Because public service is mostly monopolistic – only one first class postal service, only one Medicaid, only one DMV and road system, only one school system – and funded from taxes which are not voluntary, public service labor unions are themselves basically legally protected monopolies. If the teachers at the local elementary school demand something and the parents do not want to meet those demands, the parents have nowhere else to go to get their children educated unless they accept having to pay double – the taxes that go to the elementary school and the tuition that pays for a private alternative.
In contrast, if Toyota's auto workers demand something from the company and costumers don't believe they should receive it (for whatever reason), they can go to Ford or VW and not have to keep buying cars from Toyota. This is a huge difference. This is what permits public service labor unions to hold their costumers over a barrel – public school teachers will continue to be paid even if the parents of their pupils no longer want to deal with them. This is why some citizens are complaining about public service unions in particular, not about unionized labor in the private sector. And this is also why public service laborers are able to pull down such hefty pensions – there is no one else offering their service so their terms have to be met.
But from all appearances the members of the public service unions throughout the country, most visibly now in Wisconsin, speak as if they were members of plain old labor unions, comparable to unionized workers in the private, competitive market place (e.g., auto workers). This is an understandable tactic. Most Americans who give the matter any thought at all see unionization as a right all working people have. Not too many may exercise this right these days, admittedly, but they have it, just as you and I have the right to sing in our showers or travel to France even if we do not choose to do so.
So if the controversy were about whether Wisconsin's and other states' public union workers should have their right to be members of a labor union legally protected, they would be supported by most Americans. The fact is, however, that public service union members aren't at all like private sector union members. They enjoy a legally protected monopoly. And that is a violation of the rights of their customers who have nowhere else to go to obtain the service that the public service unions provide.
Maybe a comparison will help to grasp the point. Imagine that those who work at the Department of Motor Vehicles in some states decide they want longer vacations or more pay or better retirement benefits. If they do not receive these, they threaten to walk off their jobs. (In many places throughout the country they are legally forbidden from doing this, precisely because they are so different from private sector union workers.) Drivers in those states have no alternative but to deal with the DMV so the workers there will receive what they demand. There is no other option. The option of banning strikes is for most people in the country a pretty harsh, out and out un-American measure!
Clearly the relationship between public service union members and those for whom they provide their service and the relationship between private sector union members and their costumers is entirely different. But if this is acknowledged, citizens may come to view the position of the public service union members, as well as the benefits they have managed to obtain in their collective bargaining with their public agencies, very differently from how they view it while thinking the two are alike.
Not even the news agencies that report on the current conflicts in Wisconsin (and very possibly in neighboring states) appear to appreciate the difference between public service and private sector unionization. Yet this is a vital fact and understanding it would change dramatically how the vast majority of citizens are perceiving the current controversy.