That's comes off as kind of unfair and misplaced. It's one thing to ask or expect others to be open-minded or have empathy for things outside of their regular circles, it's another to presume they must know details about cultures and subcultures they aren't apart of or even condemn them for genuinely not knowing about something or asking.

It's alright to not know about everything, as nobody does, and ask questions. For those concerned, they can explain the history or their views. It's a normal process of learning.