The Wisconsin legislature wants to outlaw collective bargaining. A law eliminating collective bargaining is an assault on the First Amendment. Elimination of collective bargaining would mean that the employees no longer have the ability to assemble and petition their government for a redress of grievances.
Assembly is the key to free speech. One voice can be silenced, thousands cannot. E pluribus unum. Out of many, one.
Since all laws are enforced by the police power of the state, any law that is passed carries with it the implicit threat that force will be used if it is disobeyed. Therefore, a law that outlaws the right of employees to collectively bargain outlaws free speech, under the threat of violence. When free speech is eliminated, there are few options left to a people who want to be free. None of them are pretty. The Republicans in this case have decided that if they cannot win against the unions at the negotiating table, they will simply outlaw them, and thereby eliminate their free speech rights. Free speech for everyone, as long as you say things the Republicans like.
To me this isn't a union issue, it isn't about anything other than free speech. If you allow the government the ability to silence a group that you disagree with, who will defend you when the government comes to silence YOU? Since the Republican legislature wants to silence free speech, the people (union employees are people) are protesting, and doing it in a non-violent way. The government responds by sending police to violate the rights of the protesters and ordering them to leave, and the police refuse, even though the police would be exempt from the law that prohibits collective bargaining. Maybe there is hope for the Constitution.
The only thing I am addressing with this post is the attempt to outlaw collective bargaining. This is far too large of a topic to tackle all things union. Any other topics, like how public employees being disciplined have due process rights, or any other union topic will have to wait for another day.