With a secular materialist worldview, the, "social construct," is like putty, waiting for the next bit of social engineering or theorising to explain it and mold it to the prevailing societal fashion.
I don't understand post modernism, not many do, but I think the post modernists are always coming up with new theories to explain what makes us tick, and how we can tick better.
Personally, I reject any theory that tries to explain us in terms that do not reply on objective moral absolutes.
Subjective relativity is to me a misunderstanding of our true nature.