Neither do they.
I flog this book at every opportunity. It's a free ebook (.pdf). It's the best I've seen on the subject.
http://home.cc.umanitoba.ca/~altemey/ For example, take the following statement: “Once our government leaders and the authorities condemn the dangerous elements in our society, it will be the duty of every patriotic citizen to help stomp out the rot that is poisoning our country from within.” Sounds like something Hitler would say, right? Want to guess how many politicians, how many lawmakers in the United States agreed with it? Want to guess what they had in common?
Or how about a government program that persecutes political parties, or minorities, or journalists the authorities do not like, by putting them in jail, even torturing and killing them. Nobody would approve of that, right? Guess again.
Don’t think for a minute this doesn’t concern you personally. Let me ask you, as we’re passing the time here, how many ordinary people do you think an evil authority would have to order to kill you before he found someone who would, unjustly, out of sheer obedience, just because the authority said to? What sort of person is most likely to follow such an order? What kind of official is most likely to give that order, if it suited his purposes? Look at what experiments tell us, as I did.
If, on the other hand, you’re way ahead of me, and believe the extreme right-wing elements in America are still working to take over the country despite the recent election--nay because of it--I think you can still get a lot from this book. The authoritarians aren’t going away.