Is there anything that can be done about someone refusing to be objective in the rating process?

What does your quarterly counseling say? Your NCOER should reflect your counselings. If it doesn't then there is a problem. I hope you made sure you were counseled. Until you see the NCOER there is not much you can do about it.

Honestly, I would go to IG with the complaint and listen to what they have to say. But, if you get the rating and petition it, you will have a better chance of beating it because then its a higher elchelon that will investigate bias for a performance eval. Typically, that is when it will come out and your ncoer will be modified for E7 E8 board

this is a tough one, if your talking about performance eval then youre in quite a pickle if what you say is true. Normally those are objective and reflect your professional fitness as your seniors see you. If they are using it t manipulate your career choice, it's gonna be very hard to prove it. If your already out the door though, get up with folks in your new unit and start networking with them. Chances are these leaders have called ahead and spiked your punch up there, get in with them now and leave an impression with them. You know anyone up at that new unit let them know what youre facing as well, they'll be great allies for you. Don't let this sour your career though. You wanna keep what you got and leave on a good note.