Have you ever wondered an old photograph of yourself and been discomfited at the way you looked? Did I really dress like that? Yes you did. And you had no idea how ridiculous you looked. It's the nature of style to be imperceptible, in the same manner; the movement of the earth is imperceptible to all of us walking on it. Similarly there are things you can't say!
What shocks me is that there are moral approaches too. They're just as random, and just as imperceptible to the majority of people. But they're much more treacherous. Fashion is mistaken for nice design; ethical fashion is mistaken for good. Dressing unusually gets you sneered at. Breaking moral fashions and speaking things you can't say can get you abused, disliked, locked up, or even killed.
If you could take a trip to your past in a time machine, one thing you'll observe that is, regardless of where you went: you'd have to see what you said. Opinions we think undisruptive could have gotten us in problems. So is the things you can't say!
It sounds like a continuous tradition all through the history: In every age, you and other people considered things you can't say that were just silly, and believed them so powerfully that you would have gotten in awful dilemmas for saying the things you can't say....