@fresco,
I'm afraid that's so. Nevertheless, I might insist that we are all to a degree both right and wrong. To be obvious:no perspective is omnicompetent.
I think that despite his apparently incurable inability to grasp your relativist perspective, there is some truth in his absolutist/dualist assertion that "If there is a REALITY independent of what humans can perceive it might very well be [considered] a fundamental REALITY. " Why not? I think this may apply to everything including reality DEPENDENT on what humans
can perceive: every manifestation of reality is without need of a more "fundamental" (supportive) , foundation behind, between, or below it.
And let me throw this in: This is a basic principal for mature meditation; every sensation, thought, or impulse is ultimately complete, without any need of interpretation, evaluation, revision, sublimation or justification.