All Muslims believe in one thing, otherwise they are not Muslim at all: The shahada.  
"There is one god, Allah is God, Mohammad is the prophet of god." 

One god,  one prophet, one book (Koran), one faith,  one path,  one people,  one world.  There is nothing but that.  Death to all who don't follow Allah  is the prescribed medicine.  Every pretty little Muslim girl holding a sign begging for mercy  believes that just as much as any jihad car bomb  maniac.