That's comes off as kind of unfair and misplaced, when a person is not of nor participates in activities common to a particular group. We may only see or know of a particular side of a person. We can see people, in certain settings for many years, yet not know various things about them or they don't show aspects or share various details about themselves.

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 as they come up. For those concerned, they can explain the history, details, or their views. It's a normal process of learning.