Can I be demoted without being given any reason?

I am the lone female management person at my place of employment. The state requires someone in my position to have a bachelor's degree. My position is the only one with this requirement, and I am the only person with a college degree at work. In my 22 years of service my position has always been the highest paid position due to the above information. My two male colleagues are extremely angered by this and say that it isn't right for me to make more money than them; they have been stalking me, telling my supervisor lies about my work practices, threaten any employee who is civil to me, etc., for almost three years. I have complained to both my boss and HR to no avail. My boss just told me that he is tired of all the garbage, and changed my working conditions, giving me a huge cut in pay. This now makes my salary less than my male colleagues. Do I have any recourse? Please note that I just received my annual evaluation and with a maximum grade of 4, I received all 3's and 4's--my boss had no complaint, at least to my face. Thank you very much.