I think they honestly did not know or even suspect, and actually I think they cannot grasp the concept that culture is a real, meaningful and substantive thing that permanently shapes people and determines what they believe and how they behave. Their concept of "culture" is completely hollowed out, shallow and meaningless, they think it means stuff like wearing a sari and making delicious curry; doting on your nonna and talking with your hands; or whatever other boring stereotypes you can think of.
There have been a few very good posts on the Farms about this phenomenon recently but they're hard to search for. But basically I think the reason white westerners have a hard time understanding what culture actually is, is partly because of the "water we swim in" factor but also because white western culture is generally fairly benign. Normal white western people in general do not lie, cheat, or steal with a clean conscience; we don't throw acid in the faces of our relatives; we don't murder our daughters for having foreign boyfriends, we don't band together with our siblings to systematically rape and abuse vulnerable young girls etc. We associate all of those things with "being a bad person" so when they happen and we hear about them, people automatically frame it as "Wow what a bad apple." They're not bad apples. They're not outliers at all. They're absolutely normal representatives of their own, real, cultures, which have unfortunately been welcomed into our societies.
