I am anti-union and always have been.
In context, however, it is an obvious historical fact that unions came about because basic rights of workers were abused. No different than any other democratic movement, unions represented the people inside of them. The vast majority of the protective laws and workers rights that we enjoy in the USA (most of the Western world, actually) comes from the efforts of the unions and the political parties they supported.
In the case of public workers, there is a mixed basis for the need for unions. Because much of the pay from the workers comes from the public till and the public has shown throughout history that they vote against raising taxes on themselves, there is a good argument that government workers need some sort of collective bargaining. However, because of the nature of the way governments are run - not for profit, generally non-professional managers in charge, subject to fickle voters, etc. - over the decades and decades of bargaining the pay and benefits has become too tilted in favour of the union members.
I also think to argue that the law is not a "union-busting" law is naive. To argue that it does not cut pay is also naive.
Limiting the ability of a union to negotiate for nothing more than cost-of-living removes much of the reason for collective bargaining.
Making union employees pay for more of their retirement benefits and their health care is certainly a pay cut. I think it is more inline with standard practice outside the public sector (as a rule of thumb, employers pay 80% and employees 20% of health insurance, for example), but to say it is not a pay cut is a poor position to argue from.
The requirement that unions be subject to an annual vote is no different than most corporations having a board that is voted in every year. Union leaders should be subject to their members. I am not sure is an annual test is the best, but more than every 2 years is probably too long.
Finally, public unions have been a huge source of political backing for the Democrats for decades. I expect that, as normal political human nature, that Republicans will do what they can to curtail union power. There is pretty much no downside to it. The people protesting are not going to vote for them anyways.
Michael