It makes sense if you regard humans as easily manipulatable/malleable emotional beings instead of rational beings.

Just a tiny fraction of people are able to look at their "output" in a way that isn't being almost completely shaped by their "input".

If all their inputs says that their behavior is okay, they'll regard it as okay.

Sorry, I thought you were being sarcastic about it making sense. Due to that I explained why it makes sense for someone to belive something that external objective viewers would consider irrational.