Totally agree that eating at a restaurant doesn't mean you see all the subtle ways people are douches. But the comment above was about people shouting, so I assumed that the "10% of people are rude" was meaning obviously and noticeably rude. If it's just 10% of people are impatient / distracted / not very friendly / kinda annoying. Then sure, but I don't think anyone would be surprised with such a mild claim.

And as I said, I was a waiter in a busy restaurant for over two years. And the staff spent a lot of time complaining about the job to each other (as you do) and while many customers were annoying, kept changing their orders, or were a bit drunk and laughing loudly the whole time, blah blah, I don't remember anyone ever complaining about a customer being as rude as I regularly read / see on the Internet. I never encounter a "Karen".

I've always assumed it is just that Internet focusses on the tiny number of extreme behaviours and makes it sound more normal. But then I hear people say things like 10% of people are awful to staff and it makes me think that maybe there's a real cultural difference.