Oh, thanks a lot. I think it was intended for us to hate Bellick. He was very devious and oppressive in the beginning because of his role as a warden. When things changed and he became an inmate in the Panama, he had to identify with the other side as completely as he identified with the guards which culminated in the ultimate sacrifice.
But another aspect of this research is that the inmates could get along better with the guards if they accepted that the guards are not really enemies but are just playing their role. If they accepted that the human psychology is bound to make the guards in those conditions sadistic, then they would be able to predict their behaviours and subsequently get into less trouble.