They've been raised to think that their country is perfect and above criticism, so clearly it must be those dirty foreigners taking away their freedom.

Self reflection is hard. Also, I think it's one of those things that people actually know is horrible all the way down, so once you scratch it, you'd have to tear it all down. "Oh, we shouldnt punish people for being poor" leads to "everything I own was made by a slave, basically" and people don't like that

imperialist propaganda is pretty much everywhere and most people spout it for free