Suspected discrimination with strategy for termination

I am a local Government full time employee at mid management level. Over the past 10 months my supervisor has constantly been loading my personnel file with 2 verbal warnings, 1 written warning and 1 Final Written warning (less than 2 weeks ago). Despite the false accusation made, I have refrained from responding so far until when he prepared a tricky Performance Improvement Plan to go with the Final written warning. I obviously refused to sign it. The document basically states that whether I comply or not, I can still be terminated. More over, I am supposed to be the person writing that statement. In accordance with the company's policy, I sent him a formal response, addressing in a polite and professional manner all the points that he raised, with clear exhibits demonstrating that those disciplinary actions should be removed from my file. Being the only employee of a different race, I suspect discrimination and termination strategy. I cant find a job with such a file