If you talk about women or Muslims, for example, they are objects of examination - what are they like? what do they do? They aren't participants, mostly; you don't have a lot of women and Muslims posting about it - think about it: if we want to know about Islam, why don't we listen to Muslims, who would actually know from a lifetime of direct experience? What we see is mostly from the perspective of someone looking at Muslims - they are on the outside. A predictable result of the ignorance is stereotypes and prejudice. And even prejudiced and hateful ideas are treated as 'curiosity' - the curiosity of (mostly) white males. Nobody is curious about racism or sexism, for example.
My sense is that what I see on HN, maybe unconciously, is moderated to accomodate the insiders.