He says post-modernism rejects moralizing: "you should be in a family and not have sex outside of marriage", "you should work and value the work for itself." These things are not true he says. Then he makes the huge logical leap that there is no such thing as truth.

"My book contains not truth at all. It's my argument. You can like it or not." Yes, and you could also check the footnote and go to the primary sources and review them without regard to what you like or don't like. Maybe he'd say the primary sources will reflect the biases of the time, and my reading of them will reflect contemporary biases. That just means we have to be open to new evidence. We have to invite people to refute our understanding. To me that's what truth is all about.

It seems he's either throwing up his hands and saying since human bias is everywhere let's just forget about the facts or he's using truth to mean metaphysical certitude about all historical events.