Some things are hard to figure out, but are really obvious and clear once you know them.
When a group of people all know the same set of these obvious-once-you-know-them things, this is what they call common sense.
And it can be easy to think that these things are just obvious, and that anyone who doesn’t know them is somehow defective.
When the common sense is about something like how to use a computer, or how to do a math problem, or how to use correct grammar, this tends to play out as assuming that anyone who doesn’t know the obvious-once-you-know-it things is just stupid and bad at thinking.
When the common sense is about something like knowing why a particular word hurts people, or understanding how to communicate, or something like that – it tends to play out as thinking anyone who doesn’t know the obvious-once-you-know-it thing is just a bad person who doesn’t care about others, and who must be lying or willfully failing to understand, because this stuff is *obvious*.
The thing is, it isn’t always obvious before you know it. There’s a difference between clear-to-you and obvious-to-anyone-who-doesn’t-suck.
And it’s important to be mindful of this, because *everyone* is ignorant of something that is both important and obvious to people who already know it. Everything has to be learned; common sense is learned, it’s not just some sort of automatic knowledge. And it’s not right to treat people like they’re bad/stupid/evil for not understanding everything right away.