Your experience is obviously different.
I am glad I did not have to have a union to be able to work.
Apparently it has been. The common factor that I'm reading here about all of your experiences with Unions boils down to a few things:
1. CBA (Collective Bargaining Agreement) not being followed by the Union stewards and management
2. Union stewards taking advantage of the management style being used in your past company
3. Company management being weak, almost as if they are "manager in name only" type of folks.
My experience comes from both sides of the fence when dealing with unions. When I was a supervisor, I sat the union stewards down and went over the CBA with them to remove any gray areas that may have existed and to explain my role and what I needed to get done as a supervisor. They explained how they interfaced with the company and what they needed to do as stewards.
I told them that I would prefer that the union police itself before I had to get involved. If the issue did not get fixed, I then started the proper trail to have the individual put on notice.
1. verbal (documented)
2. written
3. time off without pay (3 - 5 days depending on situation)
4. Termination
All of which were documented and signed by myself, individual in question and by the steward representing the individual in question.
I would also create "read and signs" on important aspects of the CBA and company policy (DOD civil service).
My time as a supervisor went well, there was never any legal battles, if someone got fired it was there own damn fault and the Union did not have a leg to stand on because I covered my bases as per Company SOP and Union CBA.
Now that I am no longer with Civil Service but with a contractor, my role as a Union member is to do my job, no more no less. The product I present is of the same quality as when I was civil service and active duty military. The CBA and company SOP are there for a reason. the fact that they were not being followed in all of your examples means that the failure is within the ranks of management and your Union stewards period.