I'm almost inclined to say "if you don't know, consider yourself lucky!"

Short version: sf writer Elizabeth Bear (lj user="matociquala"> posted about the issues arising from writing about characters from different cultures, religions or ethnic groups. Now I've met her and she's what I think its safe to say is a very liberal and self-aware person. But the spectacular shitstorm this set off has plumbed new depths of bile and stupidity, much of it seeming to be of the form of "actually, I'm much more politically correct than you are, so your argument is therefore wrong." But much nastier.

Your point is a good one though. It's a problem with people who assert their position out of dogma and thus see their credibility amongst their peers in terms of how dogmatic they can put themselves across as being.