I've never heard of anyone quitting because they objected to being told something which they find complicated is "simple," so this seems like a straw man.

I think a lot of people think about how best to teach complicated ideas. Maybe like me, they really aren't that smart, or even just feel like they aren't that smart, and when they read from an expert or an instructor or a professor that a thing is simple, that voice inside their head that is constantly telling them they're dumb or worthless gets louder, and they wonder if that vouce is right, and that the idea they are trying to understand is simple for people who aren't impostors and they should probably give up and shoot themselves.

Your professor used the word "trivially" in a stupid way. Similarly, technical writers and instructors use "simple" in a stupid way. Objecting to stupid language from teachers and technical writers that makes them less effective at their jobs doesn't make me a baby any more than celebrating it makes you an adult.

I don't think people who use words like this intend for their audience to feel stupid. But I don't see how they are helpful.