"In a nutshell, tell us what you think postmodernism means"
That's a lot easier to do if reference can be made to ontological positions and in doing so not having to explain ontology!
Postmodernism is a wide ranging philosophical movement but in the context of this discussion, I am referring to the process of deconstructing objective accounts of reality, and claiming they are social constructs.
A relevant example to this discussion is:
Traditionally, a 'woman' was understood to be an adult human female and a female as being one of two human phenotypes upon which survival of the species is dependent.
Postmodernist accounts zoom in on biological exceptions and the ability to redefine the words to mean different things, to claim that the only meaningful way to categorise people when it comes to sex is by people's self identities in relation to it.
Robust counter arguments to this show that the 'exceptions' (differences of sexual development, aka intersex conditions) are sex specific and you can change the definition of terms like 'woman' to include whoever you like, but this won't change the material reality of the group of what where previous called 'woman' from existing.
The response to these counter arguments usually involves either nonsense 'science', accusations of evil intent, and/or appeals to be kind.
As I've said previously, objections to postmodernist accounts are not always (I would go as far as saying rarely) motivated by hate or lack of acceptance.
Many (most?) people want and expect honesty, even when the truth is difficult. Many (most?) don't really care about trans issues. What they care about is being able to speak the truth without being others wrongly accusing them of hatred. They want politicians to handle sensitive issues compassionately and thoughtfully with honesty and integrity. Saying woman can have a penis doesn't demonstrate this, neither does saying 'I refuse to answer this 'bad faith' question. The question is a test, and without showing you can speak the truth and honour competing interests, you fail the test. The democrats failed the test