every ethnic group has had to assimilate and earn the trust of fellow citizens over long periods of time...it took 200 years for a Catholic to be elected President....we may indeed welcome a muslim president at some point in the distant future when many muslim americans have proved themselves more loyal to America than to Sharia and Islam. The current climate of distrust and also the Islamic tenet of taqiyya as previously mentioned, are legitimate reasons for Dr Carson's answer. I don't think it will cost him votes with most reasonable people.