Kelly, unfortunately sometimes this happens – just concentrate on the nice affiliates to work with as they will bring the company a bigger profit and make more commission themselves.
I would simply ask the affiliate who is rude to explain his/her reasons for their issues/opinions in an email so you can show to the senior management.
If the affiliate is decent at all, the affiliate will actually take the time to provide valuable feedback. After all, feedback is crucial to all operators providing a better service to their affiliates and players alike.