It Is scripture that gives us right and wrong, not the culture of any time. What the culture tells us is what the scripture is addressing. As an example, there are scriptures about how long men should wear their hair. It is important that we know the culture of the time and what it meant in that culture to have long hair.
I think he just meant to examine the cultural thinking of the historical works we're studying, so we understand what we're reading.
You said we should study history, and I think he was just adding to that, and saying we should also pay attention to the culture of historical writings. Cultural insights often help us to understand what people MEAN when they say certain things. It just helps us to avoid misunderstandings. (It's like when my first British friend asked for chips and I brought him Doritoes. I just didn't understand him.)
I ran into this a lot when studying Karl Marx.
His fans say he's accused of saying things he never said, and that's true... sort of.
He simply used strange euphemisms for things, which, without some study, we'd never understand.
So Karl Marx DID say all kinds of horrible things, but you only get that if you first study HIM PERSONALLY, to see HOW HE EXPRESSED HIMSELF.
I think we'd all agree that some cultural understanding helps us better evaluate what we're reading.
And I also think we'd all agree with you, when you said biblical truths are more important than culture.
.