There's a great Primo Levi quote about this that I think still rings very true today, especially for those living in the imperial core:

It is true that the great mass of Germans remained unaware of the most atrocious details of what happened later in the camps: the methodological industrialized extermination on a scale of millions, the gas chambers, the cremation furnaces, the vile despoiling of corpses—all this was not supposed to be known, and in effect few did know it, up to the end of the war. Among other precautions, in order to keep the secret, only cautious and cynical euphemisms were employed by the official language: one did not write “extermination” but “final solution,” not “deportation” but “transfer,” not “killing by gas” but “special treatment.” Not without reason, Hitler feared that this horrendous news, if it were divulged, would compromise the blind faith that the country had in him, as well as the morale of the fighting troops.

And yet varied sources of information were available to most Germans. Knowing and making things known was one way of keeping one’s distance from Nazism. But most Germans didn’t know because they didn’t want to know. Because, indeed, they wanted not to know. It is certainly true that the German people, as a whole, did not even try to resist. In Hitler’s Germany a particular code was widespread—those who knew did not talk; those who did not know did not ask questions; those who did ask questions received no answers. Shutting his mouth, his eyes, and his ears, the typical German citizen built for himself the illusion of not knowing, hence of not being an accomplice to the things taking place in front of his very door.

There is so much information available that it's impossible to stay ignorant unless it is done willingly.