He should have made his participation conditional on being shown previous games. I'm pretty sure everybody outside of IBM would have considered that fair.
IBM reminds me of a kid at school that would play everybody that was playing chess up until the point where he'd win once against them. Then he'd run off and spout to everybody that he was now better than 'x'. The rematch offer was pretty lame after the cheating accusations, they should have addressed those first. No rematch given those conditions, no prior data -> no fair victory.
If IBM wanted to do this fairly they'd give Kasparov at least as much data on Deep Blue as they had on Kasparov.