It is impossible to objectively remove oneself from his life experiences. It doesn't matter if this is the right way to perform justice or not - it is impossible to perform justice in this manner anyway.
That which has been seen cannot be unseen.
That which has been heard cannot be unheard.
That which has been felt cannot be unfelt.
That which has been experienced cannot be unexperienced.
Not quite what I was looking for but in the right direction. I'm assuming Rawls would agree but when you expand the conversation to a large group these biases are minimized and as the group becomes larger and as knowledge progresses the model allows for evolution. The question is can you find a point in his argument that isn't adaptable and can be refuted with his own model's inclusion of the group in the original position's "knowledge of psychology/sociology".
hints:
red headed brownish/red headed anarchist, "knowledge of psychology/sociology" (this particular knowledge can be assumed to be known by many if not a majority of citizens today.)
By the way in very odd and biologically interesting way all those statements can be invalidated but in the broad sense lets assume them to be true in the majority of cases.