Rav Moshe Schapiro asked: Why is the notion of the Jews being the Chosen People not one of the Rambam's 13 Ikkarim? It is a foundation of our faith that we are chosen - is it not?
I threw this question out at shul before mincha and heard no satisfactory answers.
I have a deep mehalech BS"D to answer but I would rather hear what others have to say. And if you can't think of anything - throw it out in your shul and see what everyone has to say.