Many people automatically assume all racial/ethnic stereotypes are not only true, but everyone knows about them.
For instance you are at a restaurant and you ask the person you are with, “Are you getting dessert?”
“I’m Greek.” they say as though that answers your question.
To clarify you ask, “Does that mean you are getting dessert or you’re not?”
“Come on, not only am I Greek, but my wife is English.”
You scan the menu for clues and see not only is there no baklava on the menu, but neither are there scones so when the waiter comes to the table you ask for the check. The other party is upset. “What is this? You ask me if I want dessert, I say not only do I want it, but my wife never has dessert in the house and then you don’t get me dessert. What are you? Some kind of Indian giver?”
And then you must ask, “Do you mean Indian in a Native American way or Indian from Asia?”