People often say that they don’t understand something when they really mean that there is something wrong with that thing. “I can’t understand behaviour like that.” “I don’t understand people who…” They don’t really mean to talk about their own ignorance, but when they express their “confusion” like this, they’re actually expressing disapproval and assume that what they’re disapproving of probably doesn’t make any sense in the first place. It’s unlikely that people saying this should actually think the problem is with their own understanding.
However, it is very true that people often do not understand each other. Many things that someone else does only seem ridiculous or wrong because we ourselves do not understand what’s going on. And even if what someone else is doing really is wrong or absurd, there’s still likely a reason for them that sounds better to the person doing it than we’d imagine.
That’s why I want to say that if you catch yourself disapprovingly saying or thinking that you don’t understand something, you should stop to think about the fact that this thought is likely more or less literally true. For one thing, it’s always a good idea to ask people what their logic is. If you can think of no better explanation for something than that another person is acting absurdly or out of malice, then it’s particularly likely that you just don’t understand, as people at least constantly think that they’re being reasonable on some basis. And there’s always the possibility that you’re totally wrong yourself — because you don’t understand — and the other person is being perfectly reasonable.