I don't even know where to start with that one. An example would be internal handling of problems by church's (See The Vatican and Jehovah's Witnesses, along with Scientology)....we know OF it, but it hasn't quite stopped any of them from existing. And that's just modern examples, you can trace the history of every church and find a swath of black marks, illicit activities, outright slaughter....but they still exist, nonetheless. People would rather forget the marks, especially when the number of your particular faith total in the billions, so you must be apart of the correct faith, right?
So society can influence and blind people, especially if taught at a young age (indoctrination). See also: Patriotism. Support our troops! Vote the people in who keep slashing their benefits after they come back physically and mentally scarred!
On a similar note, Media plays a huge role in this matter. Organizations like Fox News fought and won for the right to lie. There are plenty of non-disclosure agreements going around, lawsuits to financially crush the opponent without needing to win out in the end, and any Government is fond of the ability to disavow any involvement in black operations. What's that? The party of deregulation didn't want to ensure clean drinking water for an entire city? KEEP VOTING THEM IN! LETS VOTE FOR TRUMP!
We know it, but it hasn't stopped any of it, stain or no stain. The political situation right now just....awfully highlights how much we can ignore of reality, due to societal and media influence.
tl;dr - Stains don't matter if they aren't taken seriously by not only the individual, but the society.
I had to think about that for a little while at work. I am not looking forward to Sunday either, 1:30 to 10 PM shift. Ugh. Feet are gonna hate me.