Perhaps oversimplified...but,
I believe that Pilate was indicating to Jesus that any 'truth' that Jesus offered could be challenged or refuted. Pilate was basically denying that there are any concrete, irrefutable truths, or facts, if you prefer.
I could state that the sky is blue, but if someone is disposed to argument, they could come up with a variety of reasons explaining why the sky is not blue. It all comes down to a basis of diaglogue. If there is no area of agreement on anything, no meaningful dialogue or exchange could occur.
Basically, I take from it that Pilate was telling Jesus that there was nothing meaningful he could say to him, because or a difference in assumptions about the nature of reality.