I think in progressive spaces, the term "white" is widely used to mean "culturally middle class". And while I would prefer people just say "culturally middle class", because it's more accurate, "white" is a term that gets used widely for this idea (especially in America—I wonder why that could be...). Anyway, you will understand a lot of social justice discourse better if you understand that this is actually what people mean when they talk about "white feminism", "white leftism", and so on a good chunk of the time.