@Reconstructo,
A basic first question is why one would want to think in opposites or use these to classify anything or everything. Might it not be the case that opposites are suggested in some very common horizons (off/on, left/right, and so on) but may
not be appropriate (or at the very least not completely definitive) in thinking about other events in other horizons?
OR: contradictory classifications may be very useful and indeed necessary and indeed fruitful, but should they be taken completely seriously to the extent that phenomena are
always forced into them? This is (perhaps) what Kant was trying to say when he wrote about the antimonies of pure reason---they are not very helpful, but just the opposite because they are wrongly applied.
Even when one says that there is no absolute truth, one speaks absolutely. Does a oppositional classification (absolute/relative) make sense in this case? (One thinks of a line of questioning about Nietzsche here, or about the role of Forms in Plato's philosophy).
And why should one side of any duality be absolute values? Doesn't this presuppose, in a way, that absolutes are actual or even meaningful? We want to have some truths to be absolute and non-accidental and eternal, but this seems to tell us more about a psychological need in
us than about what occurs in the world, or perhaps about the influence of universals upon our ways of thinking.