This may be just a form of political correctness, but I've always tried to make a point of calling people what they call themselves. I always say "pro-life" instead of "anti-abortion." I once spent an entire page of a paper about the native people of Tierra del Fuego explaining why I was calling the tribes there Aonikenk, Selknam, Manekenken, Yamana, and Kaweskar instead of the much more common Tehuelche, Ona, Haush, Yaghan, and Alacaluf. When I was nearly done with my anthropology honors paper, I had to go back through and change every instance of "Native American" to "Indian" because I discovered that's what the Oneidas (my case-study tribe) prefer.

Today it paid off -- a friend thanked me for saying "one of Jehovah's Witnesses" rather than "a Jehovah's Witness."