Consider the logic of this Sura in the Quran;
Apostasy(leaving Islam) is punishable by death. Mohammed said, "Whoever changes his Islamic religion, kill him." Quran; Surah Vol. 9:57
Islam has a strong murderological base... ACT LIKE YOU BELIEVE IT OR DIE!... so then, not all Muslims are indeed Muslims. As all christians are not in deed christians..