Rights are ALWAYS contingent upon others. They are a pact with others and have no other real existence.
You would have been correct to say "rights are not perceptual concretes" because that is true. One cannot point to an object or any part of it and identify that as a right. A right is identified as the prerogative to exercise the power you possess to judge what is in your interest and act accordingly. A right is violated when you interfere with another man's ability to do that. Given that, an argument against rights is an argument against the morality of exercising independent judgement and acting accordingly.