The word "Pocahontas" when used against a non-native American is in fact an Honorific-denied. It is the same as saying, "You madam, are no Pocahontas." It is holding Pocahontas in the highest esteem and with utmost respect. In the same regard, calling someone an Einstein when they are obviously an idiot, is not an antisemitic slur, it is simply saying that that person is no Einstein. No bigoted slur intended.