Live in a “get fired for no reason” state?
Can't talk about Unions? Can't talk about wages? Can't retaliate against your boss openly?
Is this boss careless and clueless? Does this boss see themselves as somebody that has a disregard for the rules? Does this boss talk loudly about not being able to discuss wages?
Welp, record him/her. Then keep doing. Keep doing it until you are fired for it. Chances are this boss will also make it known you were fired for this reason. Then you can take him to court. Then. Profit.