That link gives some context to the tension between postmodernism and relativism. A claim that postmodernism is based on the idea that "truth is relative" is a

That link gives some context to the tension between postmodernism and relativism. A claim that postmodernism is based on the idea that "truth is relative" is a pretty severe overreach; even the most radical of influential postmodernists are going to be epistemic relativists, not truth relativists (even Derrida was baffled by accusations that he didn't believe in objective truth.)