>>509255312 (OP)Because it projects a real society that actually existed that was ruined by them.
The one of the only ways their propaganda works is by convincing everyone that things have always been this way, things have never been better and they certainly weren't better because society was homogenous and White in these countries.
To justify what they're doing they have to make it seem like this was all a veneer for some Handmaid's Tale type shit. They have to destroy all attachment to the past or idea that maybe in some ways they did things better back then to justify their relentless march for, "Progress." If they don't, there's a clear measurable field of data that shows, "Wow things were a lot better when we didn't have so many non-Whites. I wonder how that happened?"
But if they keep harping on about things like how the Irish were treated or make out everyone's great grandma to be addicted to quaaludes then it excuses the current degeneracy and dysfunction of today. Because it was always bad; it's a weird sort of neo-nihilist, pessimist dialectic that is surprisingly persuasive - probably because humans latch on to negatives far more than positives naturally.
So that's why. Everything has to have always been ugly, filthy, dysfunctional, queer, miscegenated, unsafe and awful or you'll realize as will younger generations that we don't have to live like this and that the people who made it this way all have names and addresses.