I think you may have a misimpression about what your workplace rights actually are.
The only workplace actions that are *illegal* are those taken because of what we call a "protected characteristic" (like race, age, sex, etc.), or a "protected act" (like complaining about something *illegal*).
It is not illegal to be "harassed" at work. It is not illegal to be called incompetent or stupid. It is not illegal to decrease someone's salary. None of those things are illegal.
The only time they are *illegal* is when they are because of a protected act or a protected characteristic. So if your salary was reduced because, for example, you complained about *illegal* DOT violations, that might be illegal itself.
I would review carefully what happened and what evidence you have about why it happened in light of this information. Because your original post seemed to have some misunderstandings about what your workplace rights actually are, you will want to be careful before entering into any legal action. You could find yourself without a job, and without recourse.
I hope this information is helpful to you.
Craig T. Byrnes
Disclaimer: Please be aware that I am not offering legal advice, nor forming an attorney-client relationship with you. I am not representing you, nor doing anything to protect your legal rights. If you believe that you have suffered a legal wrong, take action before any statute or limitations expires, or your right to do so may be lost forever. Good luck in your legal matter.