Just to answer Variane's question, I think where one can get into trouble is that there are many archaic terms for groups of people that still seem to circulate and there is a history of thinking about complex groups of people as a single physical characteristic. Unfortunately, most of them are slurs. By analogy, if you refer to a woman by a term for female genitalia (no matter how fond you are of that anatomy) or as an animal (even though you love female dogs), it will still be perceived as a slur. I believe, as a general rule, it is best not to "guess" but to ask as Ghostofmacbeth has done and, likewise, be told in a friendly and imformative way what name I respond to pleasantly.