I'd worked as a building custodian in a shopping centre for 17 years, thankfully we had a decent union and for the most part, good business agents (Teamsters Canada)..the employer had a definite classist attitude towards us hourly workers. As a shop steward I'd witnessed this in contract negotiations....having a general manager say that the employees didn't deserve a health plan etc.
My last GM was constantly trying to find a reason to fire me, was so petty and passive aggressive that he was disrespectful and mean to my wife in a very public manner with all of the other employees around.
Now, as a steward, I never went beyond speaking to things outside of the scope of the CBA . the disrespecting my wife caused me to leave that for another job that was offered.
the person that poached me (she took the photos at my wedding), was also the person that fired me for no cause...she disliked that my coworker and I would complain up the chain of command about others not pulling their weight.
During my dismissal-by ambush, i was compelled to sign a waiver, so I'd have no legal recourse.
so yeah...even if there are checks and balances in the system,unscrupulous people find ways around them