Yeah, unions are not about standing up to the boss.
Unions are there to protect worker rights and none of those rights involve questioning the business decisions or administrative decisions of the management.
Frankly, worker unions have abused the serious power they hold and have diluted it by protecting slackers. And they have earned their reputations.
The job of a worker is to be honest, sincere and be dedicated to work assigned to him. The job of a union is to ensure that the work assigned to a worker is reasonable, safe, legal and properly compensated (Over time, etc)