I suspect that this bloke is soaked in postmodernism. This article by Dawkins contains some insight into the anti-reality and anti-scientific mess that occurs when someone thinks that science is a social construct.
'The physicist Alan Sokal, one of the most effective critics of the postmodernist attitude to science, has summarised it as the belief that
“So-called scientific knowledge does not in fact constitute objective knowledge of a reality external to ourselves, but is a mere social construction, on a par with myths and religions, which therefore have an equal claim to validity.”
He illustrates it with following remarkable quotation from the sociologist Harry Collins:
“The natural world has a small or non-existent role in the construction of scientific knowledge.” '
Dawkins also clearly lays out that sex is real. https://richarddawkins.substack.com/p/is-the-male-female-divide-a-social
I still think that you are wasting your time, but it is your time to waste and if you are enjoying the debate, then maybe it is not a waste anyway. I don't think you'll change his mind though. 🙂