Excellent post Dan, I couldn't have phrased this better. I think Jews also use similar symbolism like using the name Edom to describe Rome, Greece and Christendom. I don't think the meaning in that case is based on ethnicity or genetics but rather on philosophical similarities. On the other hand the use of "Ishmael" as reference to the Arabs is both symbolic and literal as the Arabs are believed to be Ishmaelites.