There's pretty much nothing that you can do, I think. At the point where you are a graduate student, you have the least power in the academic hierarchy. You're not going to leave, because programs are generally not transferable and you've already sunk X years into your degree. You have no money and, what's more, you're usually ineligible for getting any money because research agencies only fund in a meaningful way tenured professors. So you're dependent on someone who has been trained to be quite politically ruthless (if not always necessarily competent) and you've a massive sunk cost. Finish your degree as soon as you can and remember that you likely have no friends on faculty - when you finish your degree, they lose cheap, experienced labour ;-)
I left a chemistry program with an MA and managed to be admitted into a physics PhD program. Such things are not impossible, but you'd better have people willing to get your back when the time comes.
I had
a) physics professors at the previous school (UCSB) willing to write letters, make phone calls
b) solid unpublished work that raised some eyebrows
c) professors on the admitting end willing to shepherd my application
