With that said, I'm still working on a disproof, even though I don't bear the burden of disproving anything. I would start from the physical laws of the universe, which can be used to determine the future with almost complete precision. That almost is due to quantum uncertainty. So the question is whether human observation can affect the outcome of those quantum events. The answer would seem to be yes, since observation can cause waveforms to collapse, etc, etc. But what caused the person to make the observation? Again, we turn to the physical laws of the universe and say that the decision was predicated on past physical states. Could THOSE physical states have been influenced by human observation? Sure, but we just keep running into the same problem ad infinitum until we get to the point where there is no human observation, and then you're fucked.
The only way out of it is to have something independent of this chain of causation, but if there is no separate self, there's nothing to break from of the causal chain and act as independent observer.