The idea that I find least entangled but still very potentially beneficial is that politics is the mind-killer. I realize it's an old sequence, and it doesn't have much traction here (since LW is ostensibly un-killed minds).
It is a powerful slogan, but it could be unpacked into people having different goals. Sometimes it is to find truth. Sometimes it is to find the policies with the best outcomes. Sometimes it is to enjoy the thrill of fighting tribe against tribe. This is actually a cool hobby when happens on a football field or basketball court, but when they are called Team Life and Team Choice and the ball is abortion then it is more problematic. Then all three gets mixed into one. It is usually better to keep these activities separate, I think that is the core lesson.
My favorite is that people get credit for updating based on evidence.
The more common reaction is for people to get criticized (by themselves and others) for not having known the truth sooner.