'"It is an obvious and well-known fact that if you are in danger of getting fired for not being able or willing to do your job, you just file a union grievance and you have instant job security" is entirely untrue.'

Since I was giving one example of how things go at one employer, it seems odd to say it's entirely untrue. Of course the contract covers all this stuff, of course both sides agreed to the contract, of course if the employer wanted to enough they could get rid of the bad apples. BUT --- it is an ongoing joke in this particular workplace that if you file a union grievance you won't get fired, or at least not for a really, really long time. And I wasn't claiming that this is an obvious fact anywhere but the one workplace, although I'm pretty sure it's fairly common in other public employment workplaces.

By the way, if there is an abusive employer I completely support the presence of a union. I'm glad I don't have to deal with any of that where I work. Our jobs are way better than we would get with a union contract.