I think that it's pretty obvious that the user that you're responding to is using the term 'homogenous' as a euphemism for "white"

Man, American politics really invades every online space, doesn't it? This is Europe, where "white" doesn't make sense as a concept. Brexit involved the UK leaving the EU over, among other things, immigration from Poland! Are Polish people "white?" Obviously it's not about "white" versus "non-white."

Then they should say white. I'm prepared to give a lot of leeway when conversing with non-native speakers but as somebody who has grown up within a culture that understands that the concept of cultural homogeneity cannot refer to native speakers of non-mutually-comprehensible languages or historically antithetical religious positions, if they choose to use the word in novel ways that's their problem not mine!

I'm not - not everything is about race. That's a pretty basic lesson that World War 2 taught us, that you should have learned.